This reminds me of an instance where my WM sorcerer counterspelled what I assessed to be a high-level spell, but then the bad guy counterspelled my counterspell and won. However, because we were playing with WM variant rules where the chance of it triggering are higher when higher level spells are used, a WM surge happened at that exact moment too and caused absolute mayhem.

A fun mechanic for spell casters to identify what is being used against them might be to have them automatically recognize any cantrips, or put it behind a low perception skill check, like DC 5 or 7, and increase the DC by 2 for every spell level or slot thereafter. In addition, the DC could be decreased by the highest level of spell known/available to that player.

This could be a special reaction only available to spellcasters that represents their instinctual familiarity with magic. I wouldn't make it cost a reaction point, but I would limit its use to something like their proficiency bonus with a LR or SR recharge.

So, for instance, a BBEG casts disintegrate(lvl 5). A spell caster in the group uses this special reaction to recognize the spell, and knows one 4th level spell. DC would be DC = (5 + (2 * ESL)) - GSL, where ESL is "Evil Spell Level" and GSL is "Good Spell Level". So being a lvl 5 spell, we would get:

DC = (5 + (2 * 5)) - 4

DC = (5 + 10) - 4

DC = 15 - 4

DC = 11

However, for that one dude in the party that took a multiclass level or two in warlock and would only know a lvl 1 spell, his DC would be 14.

Thats just my spitball answer though, but probably what I would start with.