Those are pretty good for starting off (more than adequate for playing with), and I agree with darefsky that selective gloss could look good. Maybe the carapaces and claws, as well as the Zoanthrope's brain.
Drybrushing could help bring out texture, yes, and if you're worried about overdoing it then that may mean there is still too much paint on the brush. If you try it with less paint, but more repeated strokes, you will see a nice effect gradually build up. But you shouldn't consider this 'necessary' so if you don't want to do it, don't feel it's a technique you need to use.
The main thing I would look out for on future models is mould lines. These can be filed down or shaved off with a craft knife, and doing that would make the models look a fair bit better in my view. Also, it's hard to tell from the pictures what you have done, but having eyes painted in a contrasting colour can help draw attention to the face.
With these guys, I'd recommend painting the bases, to tie them together and give them a 'finished' look. Glue and sand, followed by painting and drybrushing, will really help. If you'd like, static grass or flock afterwards are good additions. I like to paint the rims of bases black but that's personal preference.