You'r right about that, large herbivores do have relatively small feet, but they use all four legs for locomotion. If "Arthropodish" here uses its mantis-like front legs, it would move quite good. It would look a little awkward in motion, on all four, though, creepy, like some sort of insect-bat. Abdominal segments are good support for attacking stances, which is pretty good design. BTW your creature designs are superb! As a biologist, I salute you for such extraodinary knowledge of anatomy!
Believe me, it can be insulting to the artist. I don't know about this artist in particular, but I have known of many a person who gets irritated by a comment like "It looks like this other thing" and not even an "it's cool" or "good job" thrown in. Just "looks like other thing" end statement.
This :[link] is a Zergling. Personally, I really like your design. And for the record, for anyone who cares, I am not accusing you of ripping off a Zergling. They are obviously different in several areas.