There was a way to do them right. This wasn't it.And the less said about the Cybermasters the better. Terrible name, terrible idea.
Ideally, they wouldn't have killed off the Gallifreyans again (and for no real effect, other than a cheap gasp from the audience). Give us an Agatha Christie story on Gallifrey -- heck, bring in Agatha Christie to help the Doctor solve it! -- where Gallfreyans are vanishing, which isn't something that really should be possible.
Give us lots of shady Gallfreyan suspects. Make it look like murder or an industrial accident.
And then, in the final shot of the second episode, we see the silhouette of a Cybermaster announcing that whatever poor minor character who's stumbled on their lab has to be deleted and follow that up, after a moment of darkness, with the Master's deranged laughter.
For an era that often struggled to find a compelling idea, they sure wasted a lot of them, one after another, in the finale.