While true, it also takes a lot of busy work to maintain that status quo. You're constantly shifting forms, trying to keep your Double Mire and Eclipse going. Spamming your pets when possible etc.
A lot of people just prefer the path of less resistance. an Elec/Shield brute or Scrapper just runs up, uses a few powers and calls it a day. Non-Khelds are also much clearer in what you need to build for.
So I just chalk it up to ease of use. Warshades have a very high ceiling, but it takes a lot of effort. However, I am totally find with that, in fact I like it! I find all the form shifting and buff managing quite enjoyable, but I'm a guy who likes micro.