Yeah full roaming with skillshots usually is a recipe for disaster. Lv 3 mirana at 15 minutes, pudge that misses all hooks, etc.
Hell even just full roam is a bad idea in pubs in general. You see some pros succeeding at it (notail on earthshaker for instance), but they know what they're doing.
In a pub you'll just see the dude walk around, sap some xp, miss a gank and then go back to base to heal up.. hero is just a deadweight afterwards
Had a "sven roamer" the other day (ugh), he kept casting storm hammer on TA while she had refraction on (I was viper so he could just wait for me to destroy refraction) and then ping me and whine on voice chat that I can't kill her. Smart ass.