It's not ok, in the sense that you are running big ring/big sprocket crossover, which is never going to be ideal. Either way, my first reaction would be to say you are one link too short.
Far too much strain.
I think everyone knows not to run in large/large.
I've ridden large/large plenty of times. As I said, it's never ideal, but sometimes in a race situation there's sometimes not a lot of choice.
The issue is whether the chain is too tight, and it probably is.
It's absolutely fine.
So the mech is pulled just about as straight as it will allow, and you think it's 'fine'. Given that mech is already tight as a drum, how much tighter does it need to get before you would start to think about adding another link?
And the rear derailleur can still move further forward in 52/28