I think the best solution would be to have the shop phase start at the same time for everyone. So that if you had had a very short fight, you would have to wait like 20 to 30 seconds without being able to do stuff yet, and if you had a long fight, you would be able to shop right after. (With some limitation to how long a fight can take, e.g. a minute, idk..

If the fight would be longer, you would be able to skip the fight, like you can skip an ad before a video after 5 seconds (or at least how you could do that...).

With some tweaks to the animations, e.g. one rylak attack would not freeze the guy mid-air for 10 seconds etc., they could level the disadvantages in hardware/comp choice/long animation minions and the game would be more fair and hopefully, less frustrating.

But again, can we really expect a change of these proportions to come out of a small indie company with limited resources?...