ignoring the viability of specs in the current meta as this has nothing to do with their ease of play this is my list
t1
dh: no explanation needed
fury war: basically just a dam bot like dh, not much utility compared to arms so much lower skill cap
frost dk: if unholy is the sub of dk frost is the assa variant. do dmg, chill streak at good times and that’s about it
t2
assa: while im tempted to put assa in t1 because it’s very easy to pick up and play (as well as having access to what many ppl consider the best comp currently) due to the kit that rogues have baseline such as bomb, blind, vanish, cheap shot etc there is a higher skill cap than the t1 specs, a “good” assa rogue can make noticeable outplays by using these abilities well
enhance: basically a dam bot like fwar and fdk but brings a lot more utility to the table (range kick, ground, off heals, good tremor/hex usage)
ret: ret has lost a lot of its outplay abilities from the past like sac, rep (forced to spec into it but only taken in niche situations cuz fast hoj too important) dispelling cc etc you’re mainly just a burst dmg bot wheelchair. still has decent utility with kings, off healing but nothing that crazy. highest skill cap u can do are things like pre sancing cc which can separate really good rets from mediocre ones
t2.5 being specs that are conventionally considered mongo but have more utility and outplay potential than the aforementioned specs
arms war: pretty simple to play at its core but has a lot of outplay potential with so many abilities (reflect/disarm/duel/banner/pre d stancing/maximizing dps in battle while minimizing punishment etc) there are significant gaps between good and mediocre arms wars
unh dk: has a rep for being mongo but has a unique playstyle and dmg rotation that can take a bit of getting used to, also has lots of ways to help team and some outplay potential
t3
feral: bit of a harder rotation relative to previous specs, many ways to impact the game and outplay (rooting/cloning/pre bearing/kiting/off healing) a good feral can carry a game
ww: unique dmg rotation that takes getting used to, so much utility and ways to impact the game (rop/disarm/off healing/rooting/kiting) a good ww can carry a game
sv: slightly harder rotation than previous tiers, lots of outplay potential and many ways to impact the game. also have a unique playstyle (similar to old ret) where you’re essentially a ranged melee spec, this adds to the skill cap
outlaw/sub: both specs have way more utility than assa which makes their skill cap much higher, can’t win by just simply doing your pve rotation. gap between a decent and high lvl outlaw/sub rogue is massive
t4
pre legion sub: sub has become a lot more forgiving and easier to play now with multiple dance charges, a simplified rotation and pruning of abilities and spells that added to the skill cap. i think most people would agree that old sub is the most skill dependent melee to play, difference between a good and bad sub rogue is astronomical and imo sub has the highest outplay potential of all melee specs bc of the control and plays you can make with dance and previously pruned abilities like gouge/dismantle etc