Generally agree.

It's a tricky task to allow them a wide breadth of spells without stepping on other guilds' area of expertise. It's all too easy to make them just a second-rate jack of all trades. On the flip side, they can also easily become a slightly weak guild X... but with so much more. So yes, more unique utility spells and less sheer offensive spellpower.
Their unique spellcasting repertoire are the "meta-magic" spells - ones which alter the nature of spellcasting. The ability to store and modify the very nature of spells is something only a true master of the arcane can do. Delay spell, Chain spell, and Contingency are examples of this, as well as the ones which interfere with others' spellcasting.