Focus only on dmg for t12 farming?

So I'm farming Tier 11 about 10k waves right now, i found that the jump from T11 to T12 is quite big and I do much better farming T11 to 10k waves as opposed to T12. Question is, should I be focusing only on dmg improvements at this point to get further in T12 or are eHP upgrades still worth doing?

I am kinda floating around the 15-20 area in legends in tournament.