Rift is... interesting. There's four bosses in there, two of which you fight at the same time.
Despite this, the bosses are pushovers (comparatively) and not really an issue. Good loot, decent XP.
Rift's major difficulty is, as I call them, time Es. Time elementals. They're faster than you, they have ranged attacks (which is often a nasty debuff, as well), hitting them in melee hurts you, and there's going to be upwards twenty or so of the bastards in the first area of the rift. Then a few in the second, and another junkload in the third.
Further, the buggery things randomly trigger paradox anomalies, which can cause horrible or wonderful things to happen. The longer they're alive, and the more of them there are, the more anomalies get triggered and the more likely they are to trigger.
Bascially, I recommend going past it, killing Rantha, then coming back. Get another level, just in case, then give it a shot. If you've got decent healing, you might be okay. If you're a ranged class, you're probably in a lot better shape than a melee class is (The retaliation damage stacks bloody quick).
The rift is doable, but it's dangerous. If you're not confident, be free to skip it. It's not as dangerous as the crypt (enjoy! It's going to jump you soon~) or the spellblaze, or dreadfell, but it's a bit tougher than daikara's normal levels are.