I might be remembering wrong, but I seem to remember the majority of Dragon Age 1 party members being very mortal and/or miss-able (can't speak to the other 2 games).
Not even counting the end of the game possibilities:
Leliana can be told to bugger off, or be killed when you defile a religious artifact
Wynne can be killed as soon as you meet her, or killed when you defile said religious artifact above
Sten can be left to die in the standard doomed cozy village rest-stop, or told to bugger off at any time
Alistar can bugger off if you don't pick him to be your pretty prettiest princess, or wind up executed
The Dog can die if you don't find the medicine for it in the wilds
Morrigan leaves if you decline to have sex with her/fail to convince someone else to have sex with her.
Zevran can be killed at numerous points in the scene you meet him, and can potentially betray you later
Shale you can just opt to not find, and will betray you under certain circumstances
[Mystery Party Member] can, like many of the above, be killed as soon as you meet him
The only people guaranteed to be with you up to the end iirc are Ogryn[Who refuses to leave even if you tell him to bugger off], and [mystery member or Alistar]