Not really. I think the thing that some are having 'Issues' with is the fact that Jeph is moving what were once essentially background characters into the foreground and lessening the interaction of the 'Original Core Cast Characters'.
Remember folks, we have had shifts before, the departure of Raven, Amir, Nat, Sara and Angus. The falling into the background of characters such as Steve, Sven, Wil, Penelope and others as Jeph moves the stories forward or feels the need to change/chop or delete characters that have, to a certain extent, served their purpose or he feels need to go to make room for newer characters and storylines.
Marten and Faye are, to a large extent, the Main Core Characters of the Comic, along with Dora, Pintsize and others who have come into the picture while others have moved back into secondary roles but are seen as part of the Core of the Comic as time moves on.