Well, first off, no, you don't get the free slime from the Belcher because you already established the Belcher was silenced.
Secondly, this is just another example of magical thinking where you invent scenarios where you come out ahead. You're assuming you can dump your hand to gaurantee the KT. You're assuming you have the correct minions on board the answer any potential threats. You're assuming that your opponent doesn't have anything on his current board that you have to immediately respond to. Youve even assumed the perfect setup for KT with the 3/1 belcher. For every magical thinking scenario you come up with, I could think of 5 where it doesn't make any sense to play the card.
Well yes, you play it when it makes sense to play. Of course there are a ton of scenarios when playing it wouldn't make sense, and in those scenarios you simply don't play it. There's a ton of scenarios when playing Sylvanas + Reincarnate doesn't make any sense, and I don't play the cards in those situations.
It shouldn't be very hard to dump your hand, you've already played your early game during the early turns, you aren't holding 1, 2, or 3 drops for the 7th or 8th turn when you're ready to combo the spell. So your hand should just be high cost minions at that point, preferably one or two of the ones that do combo well with it.
But I play Shaman a lot, and I run KT in my Shaman deck, and there are a lot of times where if I could get KT out a little earlier it'd be a huge help. Right now I do think the best uses of it are with KT and Malygos.
When I try the card, I will think of it mainly as a KT combo card, much like how I think of reincarnate as a devastating MC combo card with Sylvanas. Slyvanas + Reincarnate single-handily puts any control deck in serious trouble, given you allocate your two hexes and earthshocks appropriately for the deck you're playing against.
I remember when Shaman's reincarnate was revealed from Naxx, people thought it was a weak card too, but it certainly has proved its worth to me. I can play any control deck and know in addition to two hexes, I have a 3rd answer to some incredible legendary, that itself requires either a complete board clear, or 2 answers of their own (one for what I stole, and one for the remaining Sylvanas).
