I would hardly call Jim Steinman a "ghostwriter". His name is on some of the album covers. A "ghostwriter" to me is someone like... Jake E. Lee on Bark at the Moon. Or Michael McDonald on "I'll Wait" by Van Halen (though he's getting credit now, I believe).
I would not also call Bernie Taupin a "ghostwriter" or even an "outside writer". He actively collaborates with Elton, and he is at many of the recording sessions and even toured with him in the 70's (I don't think he does now). Interestingly, TAUPIN wrote the lyrics to one of Heart's biggest songs: "These Dreams". (He also co-wrote the classic, legendary, "We Built This City" by Starship).
As for Aerosmith, I believe it was their time on Geffen Records, when John Kalodner John Kalodner got involved, following "Done With Mirrors" which was good but didn't light up the charts. "Permanent Vacation" was when the outside collaborators really dug in.
Cheap Trick is another band - like Heart and Aerosmith - that went through an "outside writer" phase. That's why we're lucky enough to have "The Flame" (single from "Lap of Luxury") and the follow-up album, "Busted".