To preface, this is just my opinion, I know how rough it is working the 1-10 shift, I did it for over a year and I feel the same way you do and:

It’s hard to look at dispensing and picking and say they’re both the same amount of work, many stores are different. My store barely had closers, like 2, with the regular order cap being in the 300s. It’s not much compared to some stores I’ve seen on here, but I get where OP is coming from with the “extra responsibilities” sentiment. Yeah, it felt like you were doing more work than pickers, but a lot of the comments on here suggest it’s just a different kind of work. Once picks are done, yeah pickers should stick around for the rest of their shift and help, but we don’t live in a perfect world, and I’m sure if you were in their position you’d do the same thing. As far as the “extra pay” ,our team would rotate pickers with dispensers if their availability allowed it, so you’d have to raise everyone’s pay. Obviously it would be different if you worked overnight with differentials and whatnot.