Positioning meant everything forever. Positioning means everything now.
The game was very enjoyable for wizards - for melee it was not unless you had a shadowmourne and 2 healers to play with, a playstyle which was an abomination. If you played anything else you had to los till you had cds up again. This was nothing close to enjoyable or fun.
Interrupts are weaker than ever with increased cds. It is secondary interrupts (stuns, silences etc) that pose a problem.
You can always outplay anyone and anything to win no matter the expansion. So no, wrath wasn't a better expansion for arena. More popular yes, better no.
Finally, although this is your opinion and I respect it, refrain from bold statements like "wrath was better" if you haven't even played MoP.
I don't think that is true at all, as a warrior i had a blast in s7/s8, could literally play with anything and make it work to at least gladiator ratings, then playing with an enhance and rdruid and stomping every LSD and MLS in sight. The ability to "outplay" people, is definitely diminishing as time has gone on, you must see that.. outplaying someone now is getting them to trinket something they maybe shouldn't have or didn't need to, then 1 shotting them in stuns or blanket silences.
I agree with your point about interupts and secondarys, i think the problem is when you have 2 melee combined tunneling a healer for example, interupts used to be (and probably still are) far too powerful. The increased CD was good for the game, but making classes like mages, and to a lesser extent warlocks and moonkins not need to cast in the first place, it gets nullfied.