I still run 2 Voodoo3's in my Network (V3-3000 and V3-3500/TV).
Those are really running quite hot as well, but they do so since years, and survived even the longest LAN sessions, without ever crashing or glitchting...
So I guess it's normal, although I remember that whether they run hot or cool depends somehow on the Motherboard they're used in.
I remember very well the day I switched from older Socket7 Boards (they almost never became really hot in there) to more modern Boards, and instantly noted those cards all of a sudden were running very hot (even in idle, no 3D used).
After losing half a dozen 486 Fans I mounted on them, I finally let them go as they were, and never had any problems.
I guess they are the most rugged hardware I've seen in my life, looks like they can easily take the heat
Greetings
FalconFly