"what class is the most fun & easiest to play" fun and easy can't go together, the Easier to play is for sure Ret paladin with Pve shoulders+legs+gurth as human with dobule pvp trinket, but ofc since you have 4 spells its boring AF, same goes for enha sham..so simply if you wanna have fun --> dont play ret+enha sham
now to the most fun...matters what you think is fun..
if you think that fun is oneshotting people every 30 seconds --> go frost mage
if you think that fun is to cc people etc -> maybe like hunter, fire mage, disc priest...actually holy in pvp is fun as well but you have to play with like full resill and play like a god (because rog's are so "skillfull" --> spam hemo and kidney every20sec and let pve procs kill you)
if you think that fun is to cancer everyone --> afli lock or resto shaman (since noone vs you will ever like you)
if you think that fun is to never die --> blood dk,feral, afli lock(with Rsham as healer at your back 24/7)
...enjoy !
PS: really, dont play ret there is more than enough of them