Again, though, we're not losing Lilies, just like SGE isn't losing AG and Kardia nor SCH AF and its Fairy... so... I don't get what the point of this exercise is. Yes... remove half of any jobs' free sustain and it will flounder. ...That is not shocking, nor unique to WHM.
Yes, that much value is spread across more systems on other jobs than it is on WHM. But that system does already exist. It's already provided. So I don't see the point in looking at a "What if..." to provide an excuse for further homogeneity.
Likewise, the game has far from switched to "twitch movement at home in a FPS or ARPG". Slidecasting hasn't suddenly turned useless. BLM, even, is doing fine (without even being particularly reliant on Paradox or its 2nd charge of Triple-cast), let alone jobs with only 1.5-2s casts.
If anything, mechanical bloat seems the larger departure from previous tiers to now (in, say, P12S).
Nor would even a lower %uptime on particular jobs be problematic so long as they were fairly consistently so across a given expansion; one could just compensate the job for that, accordingly, via the traits and actions added since the previous expansion.
Almost guaranteed to have a lower %uptime? So be it; in compensation, just give that job more of the ppm that'd depend on said %uptime, with further ability to extend over the particular problem points (be that via some sort of Ancestral Vigor mechanic or whatever else). All that matters is the parity of overall value in practice (not against a striking dummy); it does not require perfect parity in each tangential factor like the amount of free healing (which further offensive potency could compensate for a lack of), %uptime (again, which potency can compensate for), etc.
Tl;dr: I don't think that movement requirements are so bad as to cripple jobs with more than a pittance of hard-casts -- nor, especially, bad enough to excuse further homogeneity or removal of contextual depth (as by removing difficulties in uptime optimization from Melee and Casters).