Well, if we're talking like, from Canada, like LaBrie, maybe that is a bit excessive, but guys like Charlie Dominici, who lived in the same general area as them, there was no reason why they couldn't have done it in person. Or at least did it themselves, not ask their manager to.
With Derek, they already knew they were going to fire him even as they still performed with him, so they could've had the talk after the last show they did, before dispersing.
As for Portnoy, that's still not an excuse. They could've had their attorneys present, or had them follow up with the details later, but for someone like Petrucci, to not be able to tell Portnoy personally, "Listen man, you know you're my brother, but here's the situation.." is pretty weak.