getting the skill tree 4% activation time allows you to dump almost all your alacrity (i use 150), ive found a 1.8 second cast time on medical probe is the most efficient and ammo mangement done right makes it almost impossible to run out unless your team is a bunch of morons
while the only options your losing in the skill tree for weapons calibrations is either more endurance(+low self healing) or unnecessary improved ammo mangement
efficient conversions can be useful in pvp but overall isn't that important
field triage is all on choice, i feel that its not worth the 3 points and is unnecessary
and potant medicine is unmistakably needed and allows you to easily crit 6-6.5k heals
and there will always be bulid optimisations for certain situations the skill tree i posted (http://www.torhead.com/skill-calc#800rfR0RdbdkqZrcoZb.2) i find is the most all round build
my experience is 5 months+ with com healer and cleared all content