Currently list of end rewards for a 20th completion raid randomly choose the items between the whole list available. For raids that have lot of unique items like Tower of Despair a character can end with only very bad choices.
i.e a melee has the choice between savants, healers, thief acrobat rings, etc
To make it a real reward, considering the time and difficulty it takes to complete these quests the logic should be changed so that the prestige/class of the character are included by default in the list and the random factor applies only to the rest (7 out of 10 rings for ToD)