Getting interrupted is often a death sentence in PvP and almost a given if you get hit. While positioning helps, spell casting no longer has the same potency, a single cast will not substantially change the fight (except maybe Gsanc/Timestop/Mords). Wizards and other casters have been seriously gimped by systematic changes (including spell craft, ease of access of +5 weapons, prevalence of mundane friendly high magic books/gems of null/wands/scrolls). It even essentially says wizard is trash in the official Arelith build compendium lol.
I suggest either lowering the DC of Concentration checks or making it far easier to stack concentration by providing ESF Conc for free at low 20's (ideally not 27 to encourage more build diversity) for certain caster classes (Wiz, Sorc etc). This would make it actually feasible to pass checks against the current str meta's damage output (if AB's and dmg output isn't getting reigned in anytime soon).
It's far too potent to interrupt a caster's 1 of 2 or only action in the round when tempo is everything. Especially compared against "resourceless" high APRs with high AB #'s.