I play on PC, but I use a controller in addition to a keyboard. I have and don't use (in-game) my mouse. I started as a healer in FFXI and was recruited to a HNM LS (BG on Bahamut), so I'm fine with healing quickly, the targeting for healing is the same to me. I do remember holding impromptu contests of speed in FFXI, who could remove the status effect the quickest, and definitely remember a contest with more than one WHM removing paralyze from the tank at Hakutaku. I definitely remember winning that.

Targeting and healing in a hectic raid environment (targets both in and out of party) is doable, but you need to be able to shortcut to the person you intend to target. You do this by simultaneously selecting yourself and spinning the camera towards your target, then pressing left or right on the d-pad to select them. You can do this while running or casting another spell, and it is very fast. Targets in your own party are also available to be selected by pressing up or down on the d-pad, again, this is always available, allowing you to pre-select your target.

I know there are certain advantages to keyboard/mouse, being an increased number of available keys/combinations to translate to actions, but there are always limiting factors (cast times, GCDs, etc) that minimize how quickly you can input a command. Another advantage is mouse-over targeting, which (imo) doesn't have a direct translation for controller users. Still, you can abuse the aforementioned limiting factors to give you the time needed to subtarget

I find keyboard/mouse to be limiting in movement. WASD movement is less fluid than analog. Using both keyboard and mouse with camera controls to mimic analog controls, to me, is clunky. Perhaps I just don't know the necessary shortcuts to abuse keyboard/mouse like I do with a controller, I just see so much awkward angular movement (that I interpret as WASD movement [or numpad????]). It just seems like controllers users can abuse the ease of precise movement to allow for more options, whereas keyboard/mouse is requires more inputs.

But it's probably just because I'm left-handed and everything is different.