Kleft

For leveling if single target damage and pvp is priority then yes full ret is the way to go. At max? I think you will struggle to tank upper end 5 mans, the extra block chance, armour, block dmg reduction and threat from the prot tree is really useful i think. Ive never tried but many ppl say healing is fine in MC with ret talents and holy gear (you will miss out on like crit heals being free and stuff which i find fun for healing but..) Ret isnt really an aoe farming spec, pally aoe dps comes from consc (holy tree), blessing of sanc (prot) and holy shield(prot) which also buffs your survive a lot so you can take all the hits. Need prot for good aoe farming in my opinion. Reality is if you truely feel like "changing things up" in a meaningful way you WILL need to respec, but this is true of any class i suppose.

For PvE you have to be deep ret if you want to DPS. Shockadin would be ok for Healing in PvE. For PvP playstyles you have to try what you like, i often see people gushing over reck PvP, but personally i really do not like the playstyle, and like to go deep Ret. Maybe you are like me, maybe you are like the others. Also I think for PvP and PvE you might want different sets, a set with good stamina and int as well as damage stats is good for PvP (when deep ret) but not very good for PvE, which is something to consider. Im not convinced by shockadin for dmg in PvP, the cooldown on holy shock is pretty long and without good gear to stack a bunch of фекал all at once your targets not gonna die to your nuke i dont think.