That happens a lot. Comms can seem somewhat random sometimes, but that's because it can become hard to tell exactly who is doing what.
Last night's Rabanastre is a good example. I got four comms for healing and explaining the fights to our newbies. Moro got two comms for healing and literally tanking the Azure Guard on the first boss, since our tank was not interested in tanking (or mechanics, or anything). I tend to think a WHM also pulling tank duty to make us not wipe a second time is probably more worth a comm than a fight explanation, but the explanation is REALLY visible and easily noticed whereas a DPSer in tunnel vision because we already wiped once to that add may not realize who is tanking it so long as it's not them.
That's also why things like fun res macros, cool glamour, and other such mood lifters tend to get comms. They're memorable. Without a parser running I have no idea if one of our DPSers is subpar and being carried by another one, so it's pretty hard to accurately comm that.