There are only few useful Talents for mages - just don't spend these talents and you can trade them for 10 Ability points each and have a great caster that has access to every school of magic.
Imo Earth is the worst school of magic. Every class has their Elementals (Skeletons for Witchcraft), but their damage spells are relatively weak because the enemies mid-lategame often have high poison resistance. Basically you could only take Bless + Summon Spider and move on.
The summons scale with your level:
http://steamcommunity.com/profiles/...;browsefilter=myfiles&view=imagewallDeathpunch deals a ton of non-elemental damage (~1000).
Soulsap will add almost every debuff effect on the target that does not count as a status effect, including -50% resistance vs everything (elemental + regular damage).
