American comic books, the general rules are: homages = ok, parodies = ok, copying character designs otherwise = poor taste. The Deadpool/Deathstroke thing is on reason (among many) Rob Liefeld has a reputation as a hack in the industry.
Panel-for-panel copying isn't something you'd see much of in US comics, or at least notice or care about, because panel-to-panel movements are much more abbreviated, so there's not as much to copy. (Go read Understanding Comics, it has a great breakdown of the different ways panels are treated in Asian as opposed to American/European comics.) Anyway, the panel-stealing is blatant enough to notice, and that's baaaad.