Yeah, this is a pet-peeve of mine too. Back in OG EQ, I assumed this was just a tech issue, and maybe it was.
The funny thing is, we have pushback in the game for channelled abilities like Bind Wound and spells like Lick Wounds, where its evident that the bar chunks down when hit in melee. I feel this isnt present for normal spell casting but I could be misremembering.
I like the idea of pushback for all spells and abilities, but its also improved by Channelling. Could be a nice avenue for trinkets, jewellery and buffs to add to the channel skill which would be helpful for many classes.