hard to say
cant say much to summy cuz its seems they barely have any healing left so i only take a look at cleric and warden
aoe / single target
warden has stronger aoe and singletargetheals by far
pvp / pve
in pvp its hard to say while warden has stronger and more heals the cleric can give you shields which prevent you from getting any damage at all which counters brutality stat from enemys so some prefer them as heals there (even who i still prefer warden
) in pve its completly out of the question warden > all he can even soloheal new raidinstance on hardmode
hots / burst
well like said before stronger burst heal by far and a shitloads of hots he can also apply
buffs
well cleric and warden both have - damage recieving abilitys for others so i guess they are on par there but while warden heal can only provide 2 sek + 350 bloodlust every 12 sek a cleric can if i remember right give temporal acceleration so he is probably better in buffing his party
last to say 1 more thing warden has cuz of stronger heals more time to idle around so you can use this time to do quite a bit of damage and cc