Not quite, the raid sets have specific perks for the enemies they belong to.

So, that means nothing to most people, how many times have you done a heroic with void burn (for example) and you team mates a rocking -blam!-ing midi and hard light, in fact the most annoying thing about mandatory matchmaking in heroics is some (most in my experience) people ignore the perks of armour and weapons and just use what they like. This is the same for helping randoms in raids. So while your point makes sense to you maybe, again in my experience most of the destiny community doesn't care/understand the importance of certain armour and weapons for different activities.

Nope. Not warlock legendary boots it won't lol

So taking that into account, allowing this makes it unfair for the warlock as exotic boots don't exist. Good shout there bud