Can someone tell me...

[Zacewing]

Which party members get booted out and when in both games? Cause I was really caught off guard when they decided to boot out Serph, Argilla and Roland in DDS2. I know Argilla and Heat both leave the party at different points in DDS1, but are there any other times in either games when someone leaves the party?

[kufufu]

In DDS2: Well, story-wise.. all of them. However, they come back in time for the final dungeon sans the characters of Sera and Serph.
As for affecting game-play, only the three you mentioned.

I think that's pretty much it. I can't recall any other times in DDS1 that another character might have taken a vacation.

[Zacewing]

So once Gale and Cielo join, they never leave?

Guess I'll have to use a party of Serph, Gale and Cielo in both games, then.

[kufufu]

Yeah, that sounds about right.

[Blackwing Dragon]

Well it depends on where you want which character to leave.
I can't remember which party I used, but it was difficult for me. I avoided gale and cielo like the plague in the first one. Gale I discovered in DDS 2 was a redeeming character, definately not bad. they changed cielo a bit by then too but still..weakness to status ailments...really?!