I agree, Angel has had his own title, both on TV and in the comics for 5 Seasons, one "After The Fall," and one "Aftermath" but apparently, at least in the beginning, he's not going to be in any sort of condition to be the central character of the series. Almost certainly, a few issues into the season, he will recover enough to be on his own once more, then the two characters will separate, either each having their own title, or teaming up with someone else. Probably, Angel will get his crew back together,or what passes for his crew now, and Faith will get a team of her own, maybe Satsu and a couple of younger Slayers.
The same thing might happen with Buffy and Spike. At some point, he will need to take his ship off on some mission that Buffy either can't or doesn't want to join, at which time he will pair up with someone else and Buffy will pick up a new partner, at least for a few issues. Remember, this is supposed to be a 24 month series, with a lot of short arcs and pair ups, resulting in as many, if not more, issues than Buffy and Angel had combined in their respective 40 and 42 issue runs.
At least that's the impression that I've gotten from what I've read.