The tank getting hot is normal if you vape rapidly, take long hits, take several hits back to back or if the 510 connection points are dirty or wet.
Some heat transfer from the delivery device to the power device is also normal, batteries will heat up as they're discharged also.
Warm is okay, uncomfortable to hold is too hot.
Try thoroughly cleaning all threaded areas of the 510 connections / both power & delivery device, they need to be clean, dry, bright & shiny and letting it sit for a few minutes between vapes.