For people who have access to literally everything, yes, Dark is awful. But for everyone else - which is almost freaking anyone - you use what you have.
You have a strong Dark team (as soon as SSR Amon rebalance hits) and Anubis. That means you can farm all AQ5s with ease as soon as your Dark Grid is complete. How many Envy Axes have you picked up? If you have several, Berith won't need any healing since you'll be swimming in HP. Here, have a video of a full FLB Dark Grid, just lacking slvl20 -> 30 on one Hammer:
That boss would've been very dead even without being Light. Since you have Anubis, you'll hit for ~25% harder... ... in theory. But I doubt that you have full FLB Grid available to you...
But again, committing to Dark won't be necessary for you. You already have a fully functional Dark team (when SSR Amon rebalance hits), so you don't need to MT for it. Unless you want to fully commit to it.Take your pick. Both elements have a very different playstyle and these Hime play to that strength. Well, Vohu has the added benefit of being super fast, but that doesn't help when the rest of your team isn't.
You like to see huge numbers? Pick Awakened Uriel, who will Burst for 2m against everything (even Water if you can debuff it, not joking).
You like to debuff the enemy and roll over it through means of control? Pick Vohu, but remember that she's not as effective off-element.With Anubis, I'd focus on Dark. Personally, I'd say Satan so that you can run Shingen, but others might tell you Pluto and stick to Herc for -50% Def.