I distinctly remember playing as an offensive elementalist and getting by okay most of the time, even in groups where, details for performance aside, things were pretty fine (as a FOnewm, but still, I had met a FOnewearl who was also doing quite well), but now I see the messages at the beginning of this thread, I suppose that changes were made on this server to raise the monsters' resistances, sadly for magic users of that type.
Caves are good (or were) to use magic in, especially when you solo, but even in teams, you have your SI techs. In mines, Magical Piece + Gifoie, is not so bad, even if you're not a FOnewm, normally. Complete with Iggy (Ignition cloak) and gifoie merge. Other nice items are Sorcerer's Cane and Red Merge. In Ruins, when you face many enemies, and especially when you solo, techs are a good choice against packs. Eventually, you'll learn when to use echs and when to shoot or slice. This takes time. Offensive techs don't have to be restricted to their stunning function.
A good megid in ep2 is great. You don't really need the hell special and might as well forget about it altogether, unless you really want performance (although, if you look at the formulaes and resistances, you will see that Megid can sometimes do better!), at the expence of other things like inventory place (30 items is really not enough...). Other techs can sometimes be good in ep2 mind you.
Like I said in your previous thread, Bringer's Rifole, and Slicer of Fanatic (gotto love that SNS combo) do wonders. Think Epsilon, Gigues, Bringers, Delbiters, even Dorphons if you want to go faster; A strong SNH can even fell a group of threee ennemies!
Good luck. It's a long quest to find what work when, plus as your equipment changes, and to make it all suit your style.
Cheers