Note that the order of these effects is random, so it is possible that Renathal can buff your Health before getting eaten by the scythe. The only card that is exempt from this possibility is C'Thun, the Shattered, which always goes first.
Are you sure that the order is random? I have restarted multiple times with C'Thun, Renathal and Malchezaar and only C'Thun would take priority while the other two were always consumed.
So I think it is intended to be in this order.
Oh and Genn doesn't work either.
I'm not sure about other cards other than Souleater's for certain (I remember the Genn one being mentioned when Madness came out though) but for this interaction it isn't exactly random. Scythe removes the minions from your deck the second the game starts during mulligan, you can never mulligan any of the three minions you put in— No Renethal in deck, no start of game trigger.
I'm not sure about other cards other than Souleater's for certain (I remember the Genn one being mentioned when Madness came out though) but for this interaction it isn't exactly random. Scythe removes the minions from your deck the second the game starts during mulligan, you can never mulligan any of the three minions you put in— No Renethal in deck, no start of game trigger.
Like FortyDust said when he explained the start of game mechanic.
It's intended.