While I like the different weather depictions and an actual damage system. I have to agree with the If you can't see the enemy they don't exist argument.
The same problem exists with Starmaster, but since Starmaster doesn't have a radar screen showing the enemies relative position to you, it doesn't stand out. In fact I hadn't even noticed that issue in Starmaster until it was brought to my attention, that's how well it was disguised.
Robot Tank is another story. You see the enemy on your radar, he's right there, and the manual even suggests that you put the enemy behind you to avoid enemy fire. Had they eliminated the radar and simply given you visual clues (left or right) then the fact that you can SEE the enemy is behind you and not firing would not have been so distracting. The 360 Radar was a necessity, it was one of the "cool bits" from battlezone, so the developers had to include it. But the fact that they don't have the AI fire when they are not in your field of view just really blows the illusion.
I believe Robot Tank is technically superior to Battlezone in almost EVERY way. However it's this one thing that really breaks your suspension of disbelief and for me makes it unenjoyable. It's like a huge zit on that cheerleader you liked in high school.. She was beautiful but you just can't get over that zit....