As threatened, I've put together a chart demonstrating the explosion in Claremont's X-output from his first gig in 1975 to the end of 1985. I've not included X-Men and the Micronauts because it was co-written, and feels predominantly like Mantlo's work, but everything else is there.
It's a pretty phenomenal growth rate. And just about 900 pages of comics in a single year? That's around 41 regular-sized issues. That's far from unheard of these days, but I wonder how many writers were managing to offer up so large an output in the days before decompression?