All the cheap SSD enclosures are not getting very warm, because the SSD/thermal paste isn't transferring the heat to the aluminium case. So they are basically cooking inside.I would think that if my drives were "cooking" the cases would be much hotter than they are at any given time. Maybe I just have good heat dissipation.
So if your case isn't getting hot under heavy load then something is wrong, IMO. Unless you have a fan.