Should there be a support with only one ability that has a mana cost, ala Whitemane in HotS?
Whitemane's Q is her only ability with a mana cost, while everything else in her kit has no cost and is only gated by cooldowns. However, her Q is gated by her Desperation mechanic, which works similarly to Kassadin's Riftwalk or Kog'Maw's Living Artillery, in that every time she uses her Q in a short time, its cost goes up significantly. This means if she spams it too much, she'll manaburn herself in an instant.
I have to wonder if we should eventually have a support who does the same, having a spammable heal that is their only source of mana cost, but will burn out of mana very rapidly if used too frequently. Would this be too obnoxious due to their other abilities not being gated?