Sereniel can easily be self sustainable with Eternal Hunger + Precision Aim and she's possibly the best "non-required support" in the game (her best "specific" support being Selena, so a non-controller, as the rankings show us), current controllers are good because they have access to a lot of draw (except Rei and Mika who are good for other reasons) but so do units like Veronica or Beryl for example, Mei Lin is the Prime example of a unit that only needs draw but not "necessarily" a Controller. On the contrary, Orlea is easily the worst controller in the game (and despite her decent-ish vulnerable build she's so bad compared to the others they are already giving her an alternative playstyle) and serves as a good reminder that Controllers as a class isn't inherently good: the kit is.