The problem here is that Arena is a peculiar environment. While in PVP teams that face a DB defense are equipped to do so, in Arena they are not.
Arena has been made more difficult by DB, it’s not that suddenly people find Arena too hard in general.
There’s also the collateral problem that you can lose all the PVP match you want but when you win you win. Losing a match in Arena hinders the whole run. A run in Arena is 8/9 rather slow matches so if nothing else you’re investing time in it, and if you lose two matches you lose all the seals.