I dont think its so much that the reaver is trash... its just boring. Contagion>spread dots>die of boredom>repeat.. Cant argue with the return healing or damage reduction but the attacks lack any skill to play. Its the equivalent of the DK tank from WOW.
Plus, its always better to mitigate damage then try to heal it. Like Pal/WL gives WAY more block/dodge then what Reaver does. Granted, it doesnt give the lessen of incoming that Reaver does, warlord does give a flat 5% miss chance that helps.