I don't know whats been mentioned so far ... so might be some repeat info.
Earth (theurgist) is the only casting line in the game without a way to deal damage short of the pet spec's (spirit, enchantments - etc - which aren't really that bad though).
I've proposed fixes before in several threads, all of which were deleted to make room for skald reads or some other unexplained reason, and here is my fix ...
Take the snare/dd away from the iceline and make it a matter based earth nuke. Add a gtaoe to earth. Those two things would add utility to the utility line of albions utility caster. It would also somewhat satisfy the thought of the siege mage. There are other outlandish ideas out there to satisfy that requirement ... but they would be a lot harder to implement and get a 'hahaha ... no' response so they aren't worth mentioning.
The ice line is also somewhat lame. I think to help the ice spec line they should recieve a debuff/dd similar to an ice-wizards but perhaps make it a 20% debuff with a lower delve rather than an exact copy of the ice wizards. Also, add a pbaoe/debuff that would delve at 275ish at top level and add a 10-15% debuff to the effect. There lots of variations (snares, debuffs, stuns ... more if i put more thought into it) to the combination spells that would allow the ice theurgist to do a lot that the wizards can not (And work very well in tandem with them) while not stepping on their toes as the pure damage dealing casters of albion.
There is also a popular option to add an ice debuff or other debuffs to one of the two lines. I'm not against this, its a good idea, but i'd rather my idea

.