I have no regrets. If there is one thing I learned from playing Gacha game, it's that you are better off just being happy with what you have instead of feeling like you need every new shiny toy that comes your way. unless you are willing to whale.

According to oddsbitch, the chance of getting the rainbow you want is 50% on a double banner, even if you spend 50k on it. Which means that unless you are a whale, you are looking take in 1-2 unit of your choice from those banners, with the limited resources available to you.

Besides, if you've been playing the game long enough and spending your resources wisely, you should have enough rainbows and stable of units to be able to clear any content. And getting all the best units tend to trivialize content anyways.

I mean if you have a unit you really really want, by all means go for it(which is what I did for Ayaka on healers banner). But it's important to set your expectation in order, and realize that you won't be getting most of those units unless you are willing to pay for them... and for someone like me hoarding is just a strategy to focus the resource on the stuff you really want instead of spreading yourself too thin(of course, with the full awareness that you might not get what you want even if you hoard).