One of the key features of the re-development of the recently reintroduced CMH versus traditional MH is the efficiency gained in the ballast. Very little heat is given off the driver [compared to traditional magnetic ballasts]. The CMH ballast should be only warm to the touch. Never hot. Without the need of an incident of failure a hot CMH should be considered defective.
I miss the 400w retro-white too. They discontinued it because they made massive improvement in, desing, manufacturing, ballast, and arc tooling. Though today's 3K/4K PPF would be equivalent to a 380w Retro-White--leaving us with a -20watt difference in output, the complaints stopped with introduction of the 630w and forthcoming higher wattages, it's game over. Have you seen the crazy 98+CRI in today's 4K CMH? Tech pushed to amazing capability and tightening the race with LED and Fluorescent in efficiency.