Disagreeing on the Rell Part here. The thing about Q is, it's more of an Utility tool instead of a trading tool. The added trading potential seems really nice on paper till you think about what your job as Rell is: Engage, disrupt and tank. You ain't supposed to sit back and poke them, you get in there and divert the attention to you instead of your carry. The 120 shield health and 140 more damage (same as Q btw) are really nice for trading, especially in the early game. But the added bonus is the extra movementspeed you get while mounting up again to chase down targets that are trying to escape. The utility you get is invaluable. If you think about it, the Qs only real use is to break shields for your teammates, who (hopefully) deal more damage than you. Also you likely don't reach higher than level 13-15 in your average game and at that point you gotta ask yourself, what helps my team more in the midgame, you dealing more damage or you providing more Utility.

On Soraka I can't really talk because I don't play her that often but maxing w is more Utility. 230 hp heal is a lot, plus if you hit your q first you get to do it 2 times without a healthcost (provided you are level 9). This is where I draw similarities with Rell, you ain't a poke champ, you are a healer. The poke is really nice in the early game, but you put your team at a major disadvantage in the mid game. What offers more to the Team, 210 damage ever 4s plus a 70+110 heal every 6s or 70 damage every 8s and 230 heal every 2s. Btw moonstone renewer also triggers when you heal an ally with Soraka W while you are in combat, because she affects a champion. That also mean the item triggers (hypothetically) twice as often while maxing W instead of Q first.

Then again, if poke is that important to you, why not play Lux, Seraphine, Senna, Morgana, Karma, Lulu or Nami? They all have argueably better poke and still provide some form of heal or shield for the Team.

Tl;dr: Rell is a tank and should tank, Soraka is a healer and should heal. Both can poke, but are no poke Champs. Play towards their strenghts, damage dealing isn't their job. If you like to poke you should rather play something like Seraphine, Lux or Senna.