I collect them specifically to use as plat-lites because monday daily HATES me.
It's even worse at only 3 per turn in yet I still disagree, at least for some players. If you're not a whale then event units are practically the only game in town when it comes to Rainbow Crystals. I'm not actually that enthused about the Black Knight but my army is already fairly mature and can easily afford to squirrel some RC away here and there until the day Leona comes around.
Not a great event for me. Got a nearly perfect event unit (until I cc her anyway, at least I got some decent min cost). About 3 silvers that I don't really need right now.....
Hm...
Standard Event Farm Unit: 50% chance on 55/7 map = 3 RC
vs.
150 DC Cyrus = 20 RC
If you can handle Crystal Keeper G, you can get 12-18 DC per run for 80/8 per run, averaging to 10 runs per Cyrus, for 800/80
Event unit would need 7 copies to tie (actually, barely beat) 1 Cyrus, so 7 x 2 (50% chance) x 55/7 = 770/98
Due to Stamina being in shorter supply than Charisma (at level 200, you have like 420 Charisma but only 18 Stamina), Cyrus would be cheaper for SC usage. Of course, we're assuming non-whale so you'd basically want to combine the two when farm events come around, going for as many event unit copies on every day but Thursday. Since not every event is farm unit, Cyrus is more reliable, per se, but you obviously get many more runs of the event map in purely due to Cyrus' DC being available only one day a week.
That, and I'm personally willing to risk pursuing a mixed strategy when it comes to using my SC on gacha and refills, so I tend to hoard my SC a bit more than most people. It's rare that the spotlight is good enough to get my attention, but I was willing to blow some SC on things like the Monica, Thetis & Gellius spotlight. I'd light all my SC on fire if they ever offer Nadia+Rachel or Uzume.
can someone enlighten me why Rachel is a good pick over say, spica? I would say they are competing for the same slots.
Rachel has higher attack and range, plus a brief but powerful slow (75% for .25 seconds lol) and isn't made of paper. Spica's advantages are lower cost, higher attack speed and her Archer Attack UP buff. Until Skill AW they ARE competing for the same slots more or less.
Rachel: Attack 712 at AW MAX, Range 325
Spica: Attack 589/630 at AW MAX, Range 260 (312 during skill)
Spica's attack speed advantage doesn't really make up the massive gap in attack, and Rachel's range advantage is huge outside skill. If you're using other archers in the same deployment group this changes though. The 2nd number for Spica's attack is there in case the Wiki doesn't include her Archer Attack Up 7% buff in her stats
And then there's Rachel's Quick Shot 2 that brings her to the (nearly) same attack speed as Spica and further buffs her attack by whopping x1.7. And it is up nearly half of the time! (30s duration / 40s cooldown)