A mega pokemon should be worth = (1 pokemon) + (1 pokemon's item slot power) + (risk invoved in mega evolution speed increasing turn)
Parental bond itself, a 1.5x multiplier, is the equivalent of being Choice Banded without actually being choiced.
Take parental bond out of the equation and we are left with Mega Kangaskhan's base stats and movepool.
Risk involved in mega evolution speed increasing turn: (this is one of Mega Gengar's and Mega Alakazam's problems) there is little to none. You could be running fake out for a free turn, or power up punch to threaten out a ghost type. Kang also has the bulk to survive a hit easily, so there is vitually no risk. Also normal Khan at 80 speed is usually fastish enough for the first turn it comes out (remember you can choose when to bring it in).
So taking that out, we simply need to evaluate Mega Khan's movepool and stats relative to the average pokemon. If you take parental bond vs choice band out of the equation, then Mega Khan has a 47 BP fighting type Swords Dance, sucker punch for priority, fake out for free damage, crunch, EQ, drain punch, elemental punches incoming... Mega khan's movepool and stats are just much better than the usual OU pokemon =/
That's why I call uber.
Not necessarily. If a Mega pokemon is worth, say, 1.2 times that, that just increases the power of the average team by 0.2. There's nothing inherently wrong with that, all it does is force everyone to use their Mega slot which given the number of Mega pokemon isn't necessarily a disaster. I guess the question becomes whether making everyone use their mega slot is bad policy, and whether Mega Kanga is strong enough even for that slot that it'll dominate it.
That still doesn't warrant it being treated differently for tiering purposes. It may as well be "you can use a legendary, but only one per team also you can't use items on them". If something's broken, it's broken.
What would that actually DO to the metagame, anyway? Would it ruin it in some way?