At your level of progress, you're not going to be able to finish the doom tower, even on normal - not even close. Not only because you don't have the quite specific skills required on your main champions, but you just have 2 level 60s and your gear isn't very good yet. So it's normal that you get stuck at some point on doom tower and have no way of going any further until weeks if not months from now - focus on dungeon progress, Clan Boss progress and leveling more champions instead.
For the scarab king, besides just having a stronger team in general, you need two main things: a champion who can put AOE shields and a champion who will do Destroy Max HP, so you can do some real damage to the boss. You don't have either of those that I can see, certainly not among your leveled champions. For destroy max HP, you could just put a destroy set on some high-damage champion who you aren't really using for anything else, that's what I did - but considering your level of progress, do you really want to do that already and make that champion (Elhain? Luria?) worse in all other parts of the game? For shielding, there is also a shield set of course, but unfortunately it will only work in the first 3 turns of the fight, you really need someone who can regularly put the shield back.
i actually thought my gear for Rae was pretty good. The Sepluchar is not really geared up with anything special for sure
Rae looks better than the others indeed, but all three have the problem of low or very low accuracy and fairly low speed. If their boots don't have speed as main stat, they really should, and they need the accuracy to land their debuffs, or buff removal in Rae's case. On Rae, you might have enough accuracy that you can get it to a decent level once you land an accuracy banner, plus some Great Hall bonuses, but on Fayne and Sepulcher it's really terribly low and will result in them missing most of their debuff attempts. Which will drastically limit their effectiveness for CB and Dragon, where they would be excellent with the right stats.
THanks L9, I have truly no idea what I am doing with gear..Rae and Seplucher or periferal champions at the moment and I have not tried to maximize them. I have a Lvl 60 Kael built much like Rae but at 181 speed and a Maulie Tankard and Thenasil as the main 4 I am working with. I also have a Masoleum Mage that will probably be important I bet.