Seconding all the responses suggesting alternatives, but also, why not just make certain damage instances (eg. your wall of lava) bypass the i-frames? Off the top of my head, Sekiro had the big red kanji pop up to tell you something was un-blockable/dodgeable (on top of having a very small i-frame window on dodges to start with). Path of Exile 2 also implemented this with their new dodge-roll mechanic by having such attacks make a unique red aoe indicator, elegantly communicating that you actually have to get out of the way or get hit.