Personally, I've never cared for the enclosed flash tube. It's guaranteed to build up heat, especially if you shoot quickly as I do (often a frame every second or faster). ... to me, it's a design flaw.
You may not like the recessed tube, many don't, but it's not a design flaw.
Profoto has sold thousands of the D1/D2/B1/B1X monoblocks world wide and if there was a problem with heat we would be reading countless threads about it on boards like this one.
They just introduced their newest compact light with the same enclosed tube and an integrated LED for video work.
The B10.I bought my D1 500s when they were introduced and within a week bought the domes to replace the flat glass. I got them when they were only $75 and thought that was stupidly expensive. Now they're
$183 which is beyond belief. I've seen a lot of people shooting with the flat glass and at the price for the dome I expect to see most staying with the flat.
However the domes do make a huge difference. I use the Mola Demi, Euro, Setti and 16" Rayo, Chimera, Profoto and Broncolor softboxes with my D1s and they're fine. The light is just as even, same fall off, as with my Pro 6, Pro 7, Acutes and Broncolor heads. No heat problems and as I mentioned in an earlier post I use the D1s for their short duration at full power.