I'm not sure how I would balance the wizard. Overall I think arcane wonders has done a good job, but arcane is a little too powerful which explains both the wizards strength and the warlords weakness.
I would love to comment on this but I can not.
All these promises...
Such an interesting dilemma though for the company. The easiest thing to do logically would be to tweak the mages themselves, rather than change every card, but I guess that is not going to happen.
The issues facing the warlord are entrenched indeed, most fundamentally that it appears to be based on a couple of ideas (build a fortress, command an army) that simply do not work, given the surprisingly weak tools it has to do the job, and the striking limitations it has built in (conjurations that can't be placed next to each other, siege weapons that fire only every other turn, low mana, builders that take forever to do anything etc)
Every bit of frustration the OP feels over the apparent advantages of the wizard is mirrored in frustration over the manifest disadvantages of the warlord.
Intrigued to see what you pull out of the hat here.