Fortress is under 15 yards with 1pt and wolf companion adds 1.3 yards per point. 20 points will cap the cool down at 3 seconds.
Just to make things clear about chuck's guide, Ill explain it better.
Snake isn't a great investment of 20+ points if fortress is the only way to spread slow, it can't hit fullscreen with typical stance dancing. Timing snake with Thundergod would work but thats just a hassle. Adding 24-30 points into spirit guide doesn't make sense either, without runemaster. 250-300k defense isn't sufficient, and not using thunder slam makes it even worse. Thunder slam + snake stance would make more sense as t-slam is the best crowd control skill for barb. Either way it would allow fortress to clean the screen while stunning everything and helping keep barb alive. Life is another issue. Any points not in dexterity for attack rating should go into vitality. Barb with low life/defense will get rekt in dense areas because fortress doesn't clear quickly on its own. Hawk talons isn't going to solve that issue and any of the barb melee skills(besides earthquake) would be a significant improvement.
Sudis Murale

Sudis Murale
Glaive (4)
Throw Damage: (9 - 10) to (28 - 34)
One-Hand Damage: (9 - 10) to (24 - 30)
Required Level: 7
Required Dexterity: 65
Item Level: 19
Dexterity Damage Bonus: (0.11 per Dexterity)%
4% Chance to cast level 4 Fortress on Kill
+(11 to 15) to Maximum Damage
+(31 to 50)% Enhanced Damage
(1 to 2)% Chance of Crushing Blow
+(21 to 25) to Strength
+(21 to 25) to Dexterity
(11 to 20)% Bonus to Defense
Socketed (2)
Throw Damage: (28 - 31) to (66 - 79)
One-Hand Damage: (20 - 22) to (49 - 60)
Required Level: 25
Required Dexterity: 99
Item Level: 36
Dexterity Damage Bonus: (0.11 per Dexterity)%
5% Chance to cast level 10 Fortress on Kill
+(18 to 25) to Maximum Damage
+(58 to 75)% Enhanced Damage
(3 to 4)% Chance of Crushing Blow
+(31 to 35) to Strength
+(31 to 35) to Dexterity
(21 to 30)% Bonus to Defense
Socketed (3)
Throw Damage: (66 - 73) to (148 - 168)
One-Hand Damage: (38 - 42) to (97 - 112)
Required Level: 44
Required Dexterity: 197
Item Level: 51
Dexterity Damage Bonus: (0.11 per Dexterity)%
6% Chance to cast level 16 Fortress on Kill
+(36 to 45) to Maximum Damage
+(91 to 110)% Enhanced Damage
(5 to 6)% Chance of Crushing Blow
+(41 to 45) to Strength
+(41 to 45) to Dexterity
(31 to 40)% Bonus to Defense
Socketed (4)
Throw Damage: (92 - 100) to (227 - 250)
One-Hand Damage: (53 - 57) to (154 - 171)
Required Level: 53
Required Dexterity: 391
Item Level: 85
Dexterity Damage Bonus: (0.11 per Dexterity)%
7% Chance to cast level 19 Fortress on Kill
+(71 to 80) to Maximum Damage
+(121 to 140)% Enhanced Damage
(7 to 8)% Chance of Crushing Blow
+(46 to 50) to Strength
+(46 to 50) to Dexterity
(46 to 50)% Bonus to Defense
Socketed (4)
is probably a better weapon for mid-game, double mo can hit 50% cb (without rainbows) and still plenty of orb space. The fortress proc location is determined by where the enemy was killed, which improves kill speed in dense areas. Fortress proc + shower of rocks from
Deadfall

Deadfall
Heavy Belt (4)
Defense: (135 - 159) to (178 - 210)
Required Level: 7
Required Strength: 36
Item Level: 19
2% Chance to cast level 2 Shower of Rocks on Kill
1% Chance of Crushing Blow
+(24 to 46)% Enhanced Defense
+(16 to 25) to Strength
Lightning Resist +(11 to 15)%
Socketed (1)
Defense: (485 - 551) to (616 - 700)
Required Level: 24
Required Strength: 62
Item Level: 36
2% Chance to cast level 4 Shower of Rocks on Kill
2% Chance of Crushing Blow
+(69 to 92)% Enhanced Defense
+(36 to 45) to Strength
Lightning Resist +(21 to 25)%
Socketed (2)
Defense: (1270 - 1400) to (1595 - 1758)
Required Level: 41
Required Strength: 218
Item Level: 51
2% Chance to cast level 8 Shower of Rocks on Kill
3% Chance of Crushing Blow
+(115 to 137)% Enhanced Defense
+(56 to 65) to Strength
Lightning Resist +(31 to 35)%
Socketed (2)
Defense: (1918 - 2095) to (2403 - 2626)
Required Level: 50
Required Strength: 436
Item Level: 85
2% Chance to cast level 12 Shower of Rocks on Kill
4% Chance of Crushing Blow
+(138 to 160)% Enhanced Defense
+(66 to 75) to Strength
Lightning Resist +(36 to 40)%
Socketed (2)
would work very nice together. Kraken would provide plenty of damage without the need for nephalem weapons and glaive wouldn't benefit from strength so remaining points could go into vitality.
Erawan
Erawan
Body Armors
'LemKoCham'
Runeword Level: 83
15% Combat Speeds
5% Chance of Crushing Blow
+(144 to 171)% Enhanced Defense
(27 to 30)% to Strength
(27 to 30)% to Vitality
Physical Resist (13 to 15)%
(15 to 20)% Bonus to Defense
is perfect for body armor.
Avatar
Avatar
Shields
'IgnFulGla'
Runeword Level: 100
+1 to All Skills
45% Cast Speed
45% Hit Recovery
-(27 to 30)% to Enemy Fire Resistance
-(27 to 30)% to Enemy Lightning Resistance
-(27 to 30)% to Enemy Cold Resistance
+(172 to 200)% Enhanced Defense
(16 to 25)% Magic Find
Requirements +25%
is great once it can be acquired, otherwise
Invictus

Invictus
Gilded Shield (4)
Defense: (293 - 346) to (598 - 705)
Chance to Block: 1%
(Barbarian Only)
Required Level: 14
Required Strength: 35
Item Level: 10
1% Chance to cast level 3 Gift of the Wild on Kill
Weapon Physical Damage +(15 to 30)%
+(24 to 46)% Enhanced Defense
+15 to all Attributes
Physical Resist 2%
Socketed (1)
Defense: (1029 - 1169) to (1897 - 2156)
Chance to Block: 1%
(Barbarian Only)
Required Level: 31
Required Strength: 70
Item Level: 31
2% Chance to cast level 7 Gift of the Wild on Kill
Weapon Physical Damage +(60 to 80)%
+(69 to 92)% Enhanced Defense
+20 to all Attributes
Physical Resist 3%
Socketed (3)
Defense: (2644 - 2915) to (4760 - 5247)
Chance to Block: 1%
(Barbarian Only)
Required Level: 49
Required Strength: 245
Item Level: 51
2% Chance to cast level 11 Gift of the Wild on Kill
Weapon Physical Damage +(90 to 110)%
+(115 to 137)% Enhanced Defense
+25 to all Attributes
Physical Resist 4%
Socketed (4)
Defense: (3984 - 4352) to (7140 - 7800)
Chance to Block: 1%
(Barbarian Only)
Required Level: 57
Required Strength: 490
Item Level: 77
3% Chance to cast level 15 Gift of the Wild on Kill
Weapon Physical Damage +(120 to 140)%
+(138 to 160)% Enhanced Defense
+30 to all Attributes
Physical Resist 5%
Socketed (4)
is just fine(10% dr).
Featherclaw
are a nice boost for attack rating, especially during early charming. Putting a point into Daedalus also helps.
Nephilim
Nephilim
Boots
'ZodThul'
Runeword Level: 85
+(144 to 171)% Enhanced Defense
+150 Defense
+50 to Strength
(21 to 25)% to Strength
+50 to Vitality
(21 to 25)% to Vitality
Cold Resist +25%
+15 Life after each Kill
are cheap but prior to charms, honorific for resists will be more useful. Chuck suggested banish/lightning arena which is great. Lightning arena is really useful for this build.
Empyrean Band
Empyrean Band
Ring
Required Level: 40
Item Level: 40
1% Chance to cast level 18 Singularity on Kill
(3 to 5)% to All Attributes
Maximum Life +3%
Maximum Mana +10%
(5 to 15)% Gold Find
add nice life, singularity proc will lock out Fortress but shouldn't be a big issue.
Ring of Truth
Ring of Truth
Ring
Required Level: 20
Item Level: 20
25% Block Speed
15% Hit Recovery
(31 to 50)% Bonus to Attack Rating
Slows Attacker by (3 to 5)%
(11 to 15)% Bonus to Defense
+2 to Light Radius
,
Xorine's Ring
Xorine's Ring
Ring
Required Level: 80
Item Level: 80
+1 Projectile to Punisher
10% Chance to cast level 19 Punishers on Kill
(51 to 100)% Bonus to Attack Rating
-(3 to 5)% to Enemy Poison Resistance
are fine or +1 skill rare with proc and reanimates for meat shields.
Fortress as a main skill is kind of slow at times but its effective for farming several charms. Like Rolls said though, its better as a support skill.