As a WHM, I can confirm that MP management is OUR problem.
I only request "MP song please" (because I always forget the name) when things don't go "according to plan" like someone dies (actually 2 or more) or I die (yeah, sh*t happen sometimes) but, usually, i take the 0.5s to request it directly if I need it. And I usually ask to stop it when I think I've recover enough MP (when shroud is nearly up and/or i know I won't need more for a moment)
I just hope the bard has some MP left for it >__<; but if he don't because he used them "wisely" for requiem or peon, then I don't think he was in the wrong, I'll use a potion to keep up a bit and hope that everything goes well.