From my personal view, it would be any of the magic (Magician or Healers) classes that provide a decent AoE (both DoT and 1-time high damage). A lot of them have skills that can deal heavy AoE damage and stack 3 to 5 times depending on the skills. A pretty nice combination to have in parties when doing some heavy mob grinding.
Thief can do a pretty good job too. If you can stack a high enough Evasion, you may as well be the new tank. Sadly, they only have 1 AoE but I found that the cooldown was decent.
Engineers are like tanking AoE monsters if built correctly. Use Mechanize to get that nice HP increase and damage decrease. Cast away with the three AoE's that go nicely together and then your own heal skill in Mecha-form (haven't seen that in action yet though). Add on Iron Man (level 60 skill) and you'll get more HP increase + resistance with double damage for Sticky Bomb + Gas Bomb for 30 seconds.
Originally Posted by Lilica
I found engineers to be great at soloing due to Heavy Artillery and Precision Shot, makes picking off enemies very easy.
I liked that combo. Movement decrease and a stun to ensure they never come near me.
The only thing I hate was that Engineers have no AoE unless you use Mecha-form.