Well at least this event gives you the shop currency via bosses, so you can just continue to kill them, just not run event maps and spawn them yourself. And thus use stamina for next reissue, or other maps farming.
I wish that instead of this paid gacha stuff I will never use, they gave us free players some different bonuses for events like my birthday aka valentines, like a premium gacha with higher drop chances for 5*/6* or something. Thou in the end with my luck I would get less 5* on such pull that normally lol.