The swath of trainers being added appear to be permanent pool additions, so I don't really see the point of racing to try to roll them, especially with content being so lackluster at the moment. I had personally been largely luckless until I managed to pull Blue from Hilda's banner on a single roll recently. Did I question it or rage about it after remembering how futilely I tried for him during his Spotlight Scout? No.
See, I learned a lot from playing (and doing gacha in) Granblue Fantasy, another DeNA title. F2P players are far, far better off saving for a limited pair (whenever those happen) guaranteed from a scouting point trade (which I've dubbed a "Pokespark" for all intents and purposes) whilst reaping the benefits of the scouts done along the way. If one obtains their target sync pair before their scout points hit the necessary total? More power to them and less stress on their gem reserves.
To be honest, there's not even as much of a disparity between rarities compared to, say, Granblue. Sure, while my Karen performs innately better than a number of my units, I attribute that to her ability. I love using Tate and Bugsy because they can match strength and pulverize the competition with their abilities as well. I could NEVER say that about a Granblue R unit in the face of a SSR. This game has potential, but we need more, different stuff to do in-game. Better for me, since I'm content to just do the bare minimum each day in order to stock up on gems and amass items for the future.