In my opinion the "mini trials" get boring and repetitive very quickly. I personally like long bossfights in general, but it doesn't really work with how most bosses in ESO are designed as the lack clear phases and repeat the same mechanics over and over. I also think trial design in general got a lot worse since MOL, my favourite trial. The newer trials are too cluttered with pointless mechanics, that either do nothing but distract or allow no smart counterplay. I actually like what they have done with CR in comparison to AS, in order to make the mechanics less repetitive and more diverse. But in the end it's pretty much the same, very simple mechanics that only become a problem because the overlap like crazy. I haven't even completed vCR HM jet, but I'm already tired of that trial. I really hope the next trial will be a actual "full" trial again.
The old trials were much more interesting. Whilst I understand trash fights are not exciting gameplay with the Craglorn style ones I felt like I was progressing through and beating each boss feels like you're stepping forwards.
The mini-trials just feels like the same thing because the progression is the same boss just with extra mechanics added via the extra bosses.
I also think you can tell a better story with longer trials and potentially have more interesting mechanics like group splits or bosses which require gear swaps.