Myself I'm pretty lenient about it, I'm not one of these guys who's like "NOOOOOO THEY MADE HIM A MICROMETRE TOO SHORT/TALL THE FIGURE IS GARBAGE", and I'm generally OK with scale being "off" as long as it looks good. That said, there does get a point where it gets so wonky/inconsistent that figures from the same line look aggressively mis-scaled next to each other. McFarlane seems especially guilty of this- the Halo line's scale being completely all over the place for instance, but also 40K having the Sisters of Battle being nearly the exact same height as an Astartes. I also recall the Revoltech Evangelion Unit 05 being underscaled next to its fellow Evas, though granted as it never appears in a scene with another Eva that's hard to judge.