Given that an armored fighter has LOW AC at that point, it definitely does matter. A greatsword fighter is incredibly vulnerable, strength characters need a shield to have a reasonable level of protection.

Or, conversely, if the AB of enemies is so low that the greatsword fighter is reasonably protected then the enemies are irrelevant and the mage will be fine with or without EMA.

In short:

If enemies are tough, EMA isn't enough. If enemies are weak, EMA doesn't matter.

If the amount of complaints about certain melee-PM builds in my inbox back in the day was any indication, I'd say that the class is anything but weak even at low levels. It's all how you build it, and how you play it. Crit immunity is a powerful thing, even if it costs you your fourth attack. The right spell selection can -easily- fix that.

I'll also point out that dev crit-PM builds on 30 cap servers rely on taking some PM pre-epic to work properly.

In most single-player campaigns "lower levels" means up to level 10. Shadows of Udrentide ends at level 14. The OC at level 18 or so. Even on a melee build you need 10 levels of Pale Master to get crit immunity, and by that time the game is just about over. The handful of spells a fighter/wizard/palemaster or something gets at those levels wouldn't compensate either.

The builds that take pale master pre-epic typically sacrifice some power and convenience while levelling in return for a payoff at level 30. That style can work on a PW where you can grind levels quickly and play a long time after you hit the cap. Even in single-player mods that let you reach level 30+ though, making such a build would mean that you have a weaker, less enjoyable character for entire chapters of, say, the Aielund Saga. Not really worth it IMO.

In single-player I'd consider pale master for mods that have you start at a high level. If you start HotU with a new character and plan to play Sands of Fate after, for example. Then such a character could be fun to try out. Starting from level 1 it would likely be an exercise in frustration, though.