Mark overstayed his welcome.

Yes! I completely agree! I have been saying this since season 2 ended. Both Mark and Luke should have been killed off in season 2. Neither of them should have been back in season 3. And I think this was part of the shows problems. Bringing characters back when they should have died in their current season. It looked as if they were going to do this again in season 4 by bringing Theo back since they sort of left it open ended about his death and I think we're supposed to assume he was fine. IMO Theo should have died in season 3 and should not be brought back.

Now, the problem with bringing him back or Mark for example is that, they're continuing story lines that should not be extended any longer and Mark was one of them. All they did with Mark was stretch out his whole revenge plan throughout ALL of season 3. Big mistake and it brought down the show just a tad. Mark should have been done in season 2. They shouldn't have tried to stretch out what little story he had left.

Now, since they did bring him back in season 3, they really should have killed him early on when Weston chased him to that ship. That's where and how I think Weston should have finally put him down. So that's twice, kind of, that they kept him around longer than they should have. It kind of kept season 3 from being more fresh.

Both Mark and Luke were laughably bad villains from minute one; so of course they outlasted the much more potentially interesting likes of Mandy, Lily, the Cult Leader's wife and the big angry blonde girl. Other subordinate villains such as Emma and Roderick also were around too long, but they were both a hell of a lot more intriguing than those whiny twin clowns.

Yah his character just ran in circles season 3, there was nothing interesting about him.