Unlike an AP Yi, she has weak defense that counterbalance her damage frenzy, so no she's not OP. I find that she relies heavily on stealth in team fights. Pink wards and oracles are usually her purveyors of death.

She sucks eggs if there is a pink ward and cc or if she gets shut down hard which she does most times in mid and top lane. So no dont feel guilty

One person who knows how to use a pink ward and it's GG for Akali every team fight. She just gets focused and dies if she tries to do anything important.

Edit: Oh, yeah, to AP Yi nub up there, greater than 80% of the champions in the game have a CC capable of stopping Yi's Meditate, and AP Yi has nothing else worth/possible to CC, so, what the **** is your problem? Failing that, take ignite or an item with grievous wounds.

I don't feel like quoting
Ok, someone said she snowballs really hard. True. One double kill and she wrecks. True.
But what does she wreck, to this person?
Bot.
What in heaven's name is Akali doing bot, besides maybe ganking if mid's going well?

Akali is a weak champ and only strives off killing carries simply because they are squishy. If the carries positioned in a spot where their team could peel her off, then akali will lack the damage she needs throughout the whole game, thats the only reason why she is a solid pick mid.

step 1 buy pink ward.

step 2 bait smoke bomb

step 3 drop pink ward

step 4 profit!