I'd highly reconsider putting something as rough as -50% spell fail to not be in the "neutral" category. That looks like a rather bad one for anyone actually affected by spell fail (so... people casting spells). Bad Weather also looks like an instagib on r10, which is... potentially pretty damn unfun. Guess better have absorb swaps on the ready at all times, and not play high reaper in early heroics in wild magic areas.
Stuff:
Very Good Surge:
Target is affected by a (visible) bomb, that after 3 seconds explodes and inflicts a miniature Timestop: targets in a small area are disabled for 8 seconds, or in case of a redname or immune target, takes 30% more damage for 8 seconds.
Good:
+5d200 temp Spell Points to everyone in group that last 90 seconds.
Neutral:
You either create a stationary wild magic area around you, or create a stationary sphere that dispels the existing wild magic area in it for 30 seconds (visible: maybe a similar gfx to the Starlight zone, only.. primal, wild, chaotic).
Very Bad:
You get the "Dance, dance!" thing from Feywild Dryad raid
You summon a hostile Doomsphere (ok maybe something more tame would be more appropriate, but im evil)
I actually like random concepts, but they often are hard to pull off in video games people gotta play a lot ./ with plenty of repetition. I hope you don't go overboard with the presence and odds of these and/or in Myth Drannor. There need to be absolutely stellar good/very good effects for this system to make sense (Edit: seeing as how debilitating some of the bad ones can be).