I've been in one that is about 15-16' high, and it is nice for overlooking a longer distance. I've also seen them at anywhere from ground level to that high. May depend on how far you want to see and if you are wanting to shoot over/into the grass? Just thinking if deer walk thru the tall grass and that's where you need to shoot them, you may need more of an angle? Just a thought without seeing the setup. Also may depend on what's behind the blind, if anything. Just thinking if you're in a short tree line, keeping it below the top of trees would help to blend the blind in. In any case, the deer will likely get used to it over time anyway tho.
Also, I would highly consider making it portable if you can (i.e. on skids), which could always be left permanent, but you have the option of moving it if the deer patterns change. In that case, shorter would be better as it would be less likely to tip. Then just anchor it down.