Flamefront needs spell damage to acually kill something. Plain -100 fire pierce is certainly not enough to farm something with it with an eye closed. Even if used with Nova Shot/Barrage 10% is a kinda low proc chance.
Actually lots of similar one-elemental dedicated SSSU's like
Windforce
Windforce
Long War Bow (Sacred)
Two-Hand Damage: (154 - 182) to (173 - 205)
Required Level: 100
Required Dexterity: 1950
Item Level: 120
Dexterity Damage Bonus: (0.13 per Dexterity)%
If You Have at Least 1000 Strength:
Knockback Enemies
+25% Deadly Strike
10% Chance to cast level 10 Claw Tornado on Striking
30% Movement Speed
+4 to Maximum Damage (Based on Character Level)
10% Mana stolen per Hit
+(120 to 160)% Enhanced Damage
50% Slower Stamina Drain
Requirements +200%
Socketed (6)
,
Firebird
,
Eerie Flash
etc. are not that powerful as you might think from the first glance.