-Move shamans and druids together onto one type of 'caster leather', maybe replace intellect with something that does the same thing (call it 'wisdom') just to put the final nail in the gear downrolling coffin, and divide the demand on int accessories. Make 'wisdom' convert to strength/agility for shamans (more so for enhance), bears, and cats, and restrict the mana increasing property to ele/balance/resto.
-Put rogues and hunters back together on the same agility gear.
-Merge leather/mail back into the same armor type, and turn level 1-40 mail into plate, while giving str classes baseline plate proficiency.
-Get rid of expertise (why do melee dps need an extra stat to cap?) or merge it together with hit rating. Additionally, merge tanking stats with dps stats. Haste = dodge, hit = parry, (or just more dodge for bears), crit = spec based survivability bonus like savage defense. Blizz actually talked about wanting to do this, so who knows.
-Completely merge spirit and spellhit. The current situation with locks/mages simply having access to less gear than other casters is idiotic. Make spirit convert to hit for ferals/enhance.
-Make strength convert to intellect for paladins (100% for holy, and less for prot/ret), restrict the mana increasing aspect of int to holy. Reduce str -> attack power scaling for paladins baseline, but the same as it does now as long as you're specced into prot/ret.
Ignoring weapons and trinkets, this would simplify the following:
tanking plate: 2 specs
dps plate: 5 specs
healing plate: 1 spec
agi mail: 4 specs
caster mail: 2 specs
agi leather: 4 specs
caster leather: 2 specs
cloth with no spirit/hit: 9 specs
cloth with spirit: 3 specs
cloth with hit: 7 specs
str tank accessories: 2 specs
str dps accessories: 5 specs
agi accessories: 8 specs
int accessories with no hit/spirit: 14(!) specs
int accessories with spirit: 8 specs
int accessories with hit: 9 specs
into:
str gear: 9 specs
agi gear: 6 specs
'wisdom' gear: 6 specs
int gear: 9 specs
-And finally replace primary stats (int/str/agi) on weapons/trinkets with just attack power or spell power, so we don't have weapons with absurdly narrow use; IE agi swords, str h2h, etc, and weapons are more versatile in general like pre-cata. Make daggers viable for enhance while you're at it. Maybe break up spell damage and healing into separate weapons again.
Most people would probably say this would make gearing more boring, but really, aside from trinkets, and procs/set bonuses, it's about as boring as it can get already. For the most part, all you do put on the highest ilvl stuff you can get, barring set bonuses and trinkets, than reforge. This type of homogenization would give everyone the ability to role change easily like priests/druids/shamans have already been doing for 2 expansions, and rebalance the incredibly lopsided demand for different gear types.