Based on the changes we ve seen which classes do you think they might have the strongest burst aka huge damage in small window?

And no meme stuff like pt firefall thing which thank god is getting removed.

It kind of depends how short a window we're talking about. Are we talking about a couple GCD's only (e.g. when trying to burst someone down in a ranked pvp match before the healer and tank can respond), or a longer window of 10+ seconds in which a tight dps check needs to be passed (e.g. burn phases in some operation mechanics). In either case, I think PT's still make a very strong contender:

In the former case, AP will always be one of the best. With Thermal Detonator being pre-applied, rockets off the gcd and a very powerful autocrit in Energy Burst they can do incredible damage in even a single GCD. Add fuel on top of that and Power Yield which will instantly build 4 Energy Lodes. I don't think any class is going to be able to compete with that.

If we're talking about longer burst windows, Pyro still has a pretty good claim. Sure Firefall is gone, but there's still the tactical which increases your flame attacks critical chance to 100% under Fuel. That turns Pyro into an absolute monster for 15 seconds. Though Pyro is definitely hurt the most by the loss of Firefall, as Fuel would make it a guaranteed crit for them.

Overall I fully expect AP to remain the king of burst. Yeah Firefall will be gone, but even without they have some amazing burst. I mean being able to throw out two autocrit Energy Bursts back to back? With TD and Shoulder Cannon in there as well? Yikes.