Really good groups that know the actual 5km will have one Cruiser with high Threat Control designated as Main Tank (usually abbreviated to MT). The MT's role is to establish aggro and kite Donatra. The rest of the group will wait a few seconds before following Donatra and as a group whack on her rear shield. Typically it takes no more than 1 minute to take down Donatra using this tactic and the best I have seen can take her down in 20-30 seconds.
That only works if you have a cruiser on the team. Even running STFs with people from the EliteSTF channel, I still get all escorts or escorts and a carrier* more than I get mixed teams with a cruiser, a couple science, and the rest escorts. An escort can
hold aggro at that distance, but they're too easily whacked out of the sky.
I need to level my engineer and build a tank with her (won't work with my current level 50 tactical). I just don't want to play through the episodes again, and it's taking forever otherwise.
*I really do not like carriers in STFs. The pets are nearly invisible, and the sheer numbers of them lag the game on my end. And then there's the one Infected Space where the carrier's pets blew the optional...