Yup, usually the rule of thumb is hitting with a single unit (a lvl 1 against a seed bearer) to any boss. Unless it's 45-15min to expire, in which case, it might be better to nuke. While it's true some players finish their oown bosses, there are also people that fire and forget, thus they expect some ally to kill it, so nuking when the timer is low is not frwoned upon.

Btw, since i play at night, i'm one of those "fire and forgeters", i usually try to nuke my own boss to 50-30% so it can be killed by someone whn the timer is low as i'm not gonna get up at 4 am to finish it =.=

PS: How do you get so many seed bearers? I haven't found any for months ;_;