I've run Vaporeon on my singles team for a really long time, and she's one of my staple team members.

I run Wish/Protect/Scald/Ice Beam with Leftovers. Investment fully into HP and DEF with the extra point in either Sp.A or Sp.D. Her Sp.D is high enough naturally that you don't have to worry TOO much about special threats, and the investment in physical DEF turns a lot of 2HKO neutral hits into 3HKO, and with Wish that means Vaporeon becomes a LOT more of a problem to deal with for them.

I guarantee that you'll get MUCH more milage out of Wish than you'll ever get out of Aqua Ring, I've tried. And Wish thrives on Vaporeon specifically because of her huge HP pool, you can easily use her wish and swap out into one of your other Pokémon and if they don't die in 1 hit from the switch, chances are very high they'll be full healed at the end of their switch turn. On top of that, for Vaporeon herself you can just use Wish to Protect to guarantee you get your HP. You can also use this to play mind games with your opponents, use a Wish-Protect to set the precedent and then next time you use Wish you can follow with Scald or Ice Beam when they expect a free turn because of Protect.

I tried Scald and Toxic instead of Scald and Ice Beam for a while, but I often ran into situations where I would have rather have a burn on something that I already poisoned. I found that I get more utility out of Ice Beam's coverage since Scald's burn chance is relatively high on top of it being a fantastic STAB attack.

I'd highly recommend at least trying out this set, I had the same thoughts as you did on Wish for a while: I didn't like waiting for the HP. But after trying it, I don't think I'll ever go back just because the utility of being able to use it on a switch is SUPER useful.