Others have expressed that same frustration SK - so you're not alone - but I'm not in that camp. For me - the changing metas keep things fresh. Yes - toons get sharded that aren't used anymore (both my Wraths are sitting on a bench right now) - but because 4-6 shards come every week I'll take the challenge of new toons and changing metas over a more static environment. I may be an exception there.
Where this DOES get potentially frustrating is feeling compelled to chase those toons. VHE is great - but Shaman - and Mystic - and Aces High are 5* Eddies as well. A variety of teams should be viable - that in itself would encourage variety - not a combination of six different toons...