Some heat is normal while charging. I've had a 2 bay for over a year, it's holding up fine.
My question is, are you noticing HEAT generally for the first time? The intellechargers tend to charge a bit more speedily than some other chargers. The two bay one does at least. You can get other chargers that charge more slowly and hence, generate less heat. It's arguable that it may be better for the batteries and you may want to look into slower charging chargers, if it's a concern.
If it is a SUDDEN, ABNORMAL, and VAST change in heat levels, I'd probably retire it. It could ALSO be your batteries getting elderly is within the realm of speculation, although I am not 100% sure it is, and if you try a newer battery and still get SUDDEN, ABNORMAL, and VAST change, I would retire it.
No point getting into potential troubles for the cost of a charger. My batteries do heat up though when they charge, some heat is normal but scorching heat is not. Etc.
Good luck,
Anna