Been able to test her for a little while and, while it's likely she may be inferior to some gold variants like Moonstruck and much less desirable than Model Leader, she's fun to mess around with.
the Charge Attack removing the enrage regardless of whether it hits or not
For starters, I can confirm that the charge attack NEEDS to land for the enrages to be consumed, just like Heavy Handed.
It is important to pay attention to the star power if you want to go for the five stacks with ease, a potentially good strat being turning it on and off repeatedly to conserve as much power as possible. As for the stun itself, 10 seconds may sound broken but it does need a charge attack and they're often hard to land. A good trick for it would be to use 4 SMs and BBs you can, finish a combo, lock the opponent into block with Slingshot and charge attack. I've also heard it Pillar Of Creation allows for charge to be used after it but still need to test it.
Here's a fun thing you can do: if you happen to somehow possess both Heat Synced and Shadow Puppet, you can inflict a 10s stun, tag in Shadow and if you happen to get lucky, reset the stun itself, potentially stunlocking the opponent.
If I had negatives to say, admittedly there wouldn't be too many about Heat herself; I believe she plays just fine and can be pretty devastating. My biggest gripe however would have to be with Annie's movement overall, it feels sluggish. I guess it serves as a compensation for her amazing kit, but it did get me killed on a few occasions.
Anyway, overall she's possibly not the most practical Annie on the line-up, but at least she can hit extremely hard. In a short sentence, it's as if Primed's SA and Summer Salt's stats combined into one