all elemental casters (poison excluded), even with great gear, are rather weak in Labs because of the absorb modifier from T6+
However if you wanna try to push an ele Druid caster far into Labs you best option is Stormfront.
You can cover 35 DR simply wit TA trophy and
Aerin Nexus
Aerin Nexus
Gnarled Staff (Sacred)
Two-Hand Damage: 59 to 62
Required Level: 100
Required Dexterity: 218
Item Level: 105
Dexterity Damage Bonus: (0.15 per Dexterity)%
+(6 to 8) to All Skills
+(25 to 40)% Bonus to Spell Focus
+50% Damage to Undead
-(20 to 25)% to Enemy Lightning Resistance
+(15 to 20) to Stormclash
+225 Life Regenerated per Second
Physical Resist (5 to 10)%
5% Reanimate as: Random Monster
Socketed (4)
and
Hide of the Basilisk
Hide of the Basilisk
Chain Mail (Sacred)
Defense: (5807 - 6817) to (6568 - 7711)
Required Level: 100
Required Strength: 600
Item Level: 120
+(1 to 2) to All Skills
30% Cast Speed
+(25 to 38)% to Lightning Spell Damage
-35% to Enemy Lightning Resistance
+(13 to 16) to Thunderstone
+(130 to 170)% Enhanced Defense
+250 to Mana
Maximum Lightning Resist +4%
Physical Resist 15%
1% Reanimate as: Random Monster
Socketed (6)
and have nice tanky Acid Fiends alo.ng with good single Target and good AoE combined in Stormfront
But if you wanna farm labs fast rather than make a point, there is no reason to choose a Caster Druid.