Kitsune Karin wrote...
Yup but that's not the main point of the manga.... And no, Kyojin's characters aside from Eren doesn't get stronger... They're still human that will be done for once a bone or two got broken...
Oh and another thing I heard about it is that the other characters aside from Ichigo are some unimportant side character with no importance.
There's more than just physical strength though. Although Eren is the only one that really grows in "power" all of the other characters still grow and gain new resolve, get over their fears or at least deal with them and grow stronger as a result.
Ichigo is usually the one that finishes the final villain of the arcs, but the other characters are still important, even if they usually can't compete with him. That's pretty similar to a lot of mangas of that genre, like DBZ and the like.