If it isn't warm, then it would be a problem. It's doing heat dissipation through the case, if the case didn't get warm after extended usage then it's a problem (hot air isn't coming out).
Electronics always get warm. Don't be alarmed unless it starts malfunctioning.
The logic board's on the right so it only gets warm that side.
(Go to ifixit and search for the iPad teardown to see what I'm talking about)