The Brummbär is meant to be survivable because of the lack of turret. If you have a skilled opponent, it is very hard to kill it, unless you manage to set up a trap. Less skilled ones will often run it into too many AT units.
Overall I think it is in an okay spot right now. Previously it had 240 armor and was deemed too weak in survivability. I think balance team is going for a middle ground here. The only thing I find obnoxious is that it is really hard to snare, simply because running at it is damn dangerous.
Bouncing three shots in a row is quite rare as Vipper said. I am not sure though if this is the correct metric. It's quite fair to assume that you have at least 2 AT units on the field that can fire twice on the approach. I think the better question is 'how likely is it for these 4 shots to pen at least twice'. At this point the Brummbar usually retreats.
So chances to pen X times out of four shots in live/preview is:
0-1 (accumulated): 6,2%/4,5%
3-4 (acc): 70,5%/75,5%
Now this attack will happen multiple times in a game (let's say 4 for the sake of it).
Beating all of them back has a chance of 77%/83% if your opponent retreats after two pens and 25%/32% if he retreats after three pens.
Additionally, all this neglects misses, so to make it short: I think you have a decent chance of encountering this somewhat regularly in the game. But on the other hand, the Brummbar cannot overextend too far because of a lacking turret.
I'd say let's see what the patch brings.
250 is ok or put 260 back and decrease speed, acc rate.
Brummbar are stock that act like doc unit. currently It perform much better than KV-2 (I've tested).
Its Speed make some medium and most TD can't catch it .They can run and kite team weapon then just retreat to safe zone with its reliable frontal armor and HP that enough to take 5-6 shot from TD. (kill strum or king tiger are easier than this)
compare with other AI unit. Let me start at KV2 because they're in same type.
-KV2 are doc unit that come with inaccurate shot specially on moving, low speed, long reload time, forever turret rotation rate(rotate a itself is faster) and expensive with very late arrived time.
other AI tank that use flame thrower not able to kite infantry or team weapon like brummbar/KV2.so I will not compare it here.