I like the idea of the totems, however I think you might want to scale that back to give extra xp/armor/hp/mp all at once, but do a % modifier like 5/7/10/extra perk or 15% sort of thing... otherwise it would be a little overpowered if a 20% flag and the 10% favor item is attained, I think you could see a level 10-12 wizard when everybody else is around 5-6.
It could still be useful if specialized in, as if it was a longer game I still think they would get to level 20, when others are around 16-17, which would be a fine reward for investing in it.
The immunity might be too much like the Oaks ability, perhaps do something along the lines of disabling an enemy hero like a polymorph/sleep where any damage removes the effect? Great run away/DG control tool!
Rather than an AOE ability, how about a drain mana ability? Unless I'm mistaken we don't have any DG's that employ that sort of attack just yet. Perhaps the mana drained could be distributed to friendly DG's in a certain range of the caster, or cause something like +25%/+35%/+45%/+55% mana regen for "15~" seconds to friendly teammates within a certain radius... has a lot of potential!
Magic armor seems good.
Melee combat could work as well - kind of a melee support wizard idea, I'm guessing your just throwing whatever numbers out, but 20 times level sounds like you would have him hitting for 750+ with a few attack items, I'm guessing that could be more like 2x, 4x, 6x, 10x?
Money purse might be a little weak of an ability, as you would sacrifice alot of utility to get it right at the start, perhaps if it was closer to 4/6/10? You might have players who go pure support role with this DG, and invest alot in the citadel, with the extra income they could buy the additional gold/xp upgrades for the team. I think several more 'pure' support DG's would be a great addition for team games.