(Cutting the quote there since Bad Breath's been addressed by others, going to expand on Death a little)
There's precedent for Death being a nuke instead of instakill. XI and XIII are both a heavy nuke with a low chance of instant kill. So BLU Level X Death in XIV could be the same, a hefty nuke with a low % chance of success, and immunity on mobs they don't want cheesed by it.
That has always been RDM's thing. They've never been able to learn the strongest white or black magics, and have never really had an involved affair with melee (push "attack", swing swing, next turn). We received a RDM that may not have been as good at filling spots as in the single player RPGs, but it still fulfills the fantasy of RDM."RDM isn't a jack-of-all-trades in this game - it's a magic caster with a melee combo that deals magic damage with a raise and a mediocre heal)."
You pull from both white and black schools of magic, you have a melee attack. They may not be as strong at being party filler in high end content as they could in single player RPGs, but they shine in places like POTD and HoH where they absolutely can fill that jack of all trades role. This plays back into the discussion with BLU where, while RDM shines in this side content, it's still a fully playable job in the rest of the game.