Personally, I just don't want to be pushed into these fights with exclusive rewards, because I simply don't find team jumprope with insta-gib and insta-wipe mechanics a very enjoyable activity. In general, I hate insta-gib mechanics, but the sheer power of healers has forced SE to resort to them more and more often to make mechanics matter at all, as they're so easily erased otherwise.

Thus, when I feel like challenging myself, I do so elsewhere, preferably single-player games. The journey towards the win is a lot less frustrating and the ultimate win a lot more gratifying there.

Other than that, so long as the development cost is justified by participation, I don't really care whether they exist or not. I don't have to like it after all. I'd just like if there were enough people who do to warrant the resources.