Well, I think his complexity might have been an intent, but it just didn't telegraph well. Durotok is right; I felt the same. I don't know that Johnson did a bad job, but he--his face, his manner, etc. is fairly non-descript. What about him stands out except he's a talented EOD guy? Not a lot.
Part of the problem IS Cranston...in that Cranston is so great, and so compelling a character that, when he's gone...well...no one else picking up the slack. More Watanabe at that point might have helped but they reduced him to saying one liners at that point too...
Ford's tough, got it. That didn't have to make him boring, and well, he's pretty boring. He could have been Chris Pine-Capt Kirk smartassy, he could have been Viggo Mortenson conflicted...he seemed none of those-(except maybe a superpowerless lesser version of Steve Rogers)...or much of anything else except dedicated to his mission...okay, fine, but nothing memorable or great. Years from now, unless Johnson emerges elsewhere as an acclaimed actor, we will struggle to remember who played Ford Brody...