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Also, Mono-Dragon dies to Scarf Terrakion just spamming CC or Stone Edge, Scizor can sit there and bullet punch once everything's softened, etc. I tried Mono-Dragon, and it was surprsingly ineffective.
Tried mono-dragon myself and its not too bad there's just a huge lack of variety. Your whole team is basically Hyper Offensive with screens latios and insert dragon like haxorus coming in, outraging, dying rinse repeat 5 times; it usually works pretty well as the enemies' steels are worn down. Also, ice weak is only problematic w/ Weavile and Mamoswine; for a mono dragon team switching is a no-no.
tbh Dragon's popularity comes from 4Drag2Mag, which obviously uses Magneton/Magnezone to kill those steel types. And obviously, the Maggys aren't Dragons.