I guess you're not the only one but there is certainly not thatmuch guys doing that. I'm focusing only on ability synergy. I don't really care about stats or girl looking. They are (almost) all cute anyway. But I'm still building teams around my favorites girls and try to found the best allies for them. And if I like some girls but they are notenough good to belong in an actual team, I use them as weak team for raid bosses.
edit: More funny stats on Mountain Lily (max def ampies, 8% 2dn level affection, max slots but not all max level equipements).
This time the target is that lvl80 event spider raid boss. Weak Pierce. The strongest raid boss from event class.
Mountain Lily deal ~5,8k weak damage with a normal attack. ~8.5k damage with a weak critical normal attack.
With counter she deals ~11k damage from a normal counter and ~25k damage with a super counter.
And she have the Guts effect. For 2 or 3 more chance to deal more counter damages, even with only 1 HP.
Now, on the same boss, Poppy (max def ampie, max 2nd affection, 2slots, 2 max level equipement and personnal equipement evolved).
She deals ~11k normal counter damage (with no weakness since she deals slice damage). And certainly arround 25k with super counter.
So, okay. Gacha girls seems to be better than event counter at higher level. But anyway, event girls are still very good for counter. Since Event counter are easier to get than gacha one's, it's still reliable to build a solid counter team.