Is that to make formation creating easier?

You can just go to the crafting screen, if you're curious who's gear is level what.

TSONE, you can get around this by knowing what crusaders are leveled and which aren't already. For example, if you never use Arachnobuddy, then why would you level up his gear at all? The only crusaders that should have ANY legendary level ups at all should be crusaders you're actually using, and if you're using them, they should already be visible on your bench to check just on mouseover. Why would you need to check the crafting screen to see who does and doesn't have legendary levels if only your used crusaders have levels? And if your non-used crusaders have levels you want to disenchant, then just go through the process of checking each crusader to fix the issue. Fix it once and you should never have to fix it ever again. You don't need a whole new game mechanic to make it a liiiiitttttlllle easier to do your one-time fix.

Simply: Typically, only crusaders that are visible on your bench should have any legendary levels. If not, fix it yourself and it should never happen again. No need for a new mechanic.

I didn't bother saying "No offense" or "With all due respect" because this can't really be said nicely. If it can, I couldn't think of a way to do so.

That sounds very defensive, and my comment clearly wasn't an opinion, but it's no matter. The topic has been resolved, regardless.