edit: oh it wasnt revealed yet. Seems pretty cool. But not great imo. Will prob be 5 mana 5/6 lifesteal, which is good if not removed. Nice to get healing in warlock tho, prob include it on that alone.
Sounds great in theory, because Warlock gets possibilities to heal, but since the discard mechanism is an RNG-Fiesta, there will be no real use for it. I already see games being decided by discarded Blood-Queens...
Warlock might have more lifesteal options so let's not dismiss it yet.
Both of them are 5 mana, have garbage stats for the cost, have a conditional Attack buff to try and make them not terrible, and are basically Silence/removal magnets. Big difference is that at least this doesn't have to be in your hand to get buffed, so that's something.
Now granted, the meta has changed a lot; BGH and Owl are no longer ever-present forces in the metagame. However, this still has to dodge a lot of hard removal before it can even get value, and discarding cards is a much more punishing condition than having your free 1/1's die over the course of the game.
Now, if your opponent does not have an answer for this in the form of hard removal, then they are completely screwed since they are either a) getting punched in the face for a decent chunk of damage and a huge life swing, or b) trading into this with one or more minions and giving you multiple heals in the process. So in a sense it creates a Tirion-esque effect where your opponent is forced to hold back some kind of answer in order to not instantly lose, and that can indeed be powerful.
So the kind of deck that could use this is a Handlock style deck; some kind of slow control deck that has a high threat density and wants something to draw removal in order to protect other more important targets. That deck also needs to want discard enablers, which is unlikely for the very same reason; you have a high threat density and therefore all your cards matter.
That's the third legendary with which they are trying to make discolock work ... kinda sad to make a huge investment (dust-wise) for such a bad deck. (owner of both clutchmother and quest speaking ... 2 clutchmothers to be precise ... (feelsbadman))