I respect you point of view, and I can't compare my Serenity with a DIV 2 board since I've never tried one, in '82 I was unfortunately still far from beginning this sport. If I'll find one Div 2 I'll surely try it. Yes we should keep in mind that in 1982 materials were so far from actual, more heavy and flexible... According to your judgement anyway I lower the vote of Serenity from 10 to 8, and give top 10 to div 2 in gliding.
About fast or not, in my still little experience the Serenity is simply serene under 4-5 knots, but becomes really imho fast in the 5-10 knots range, and not so few people confirmed this, being astonished after trying it. Yes, I'm talking about the second version of Serenity, really the first up to 2008, really different, seemed also to me to have some problems (nose always up over the water), so I don't know what version you've tested. Reaching 10-12 knots of wind Serenity give the feeling to be at its upper limit, but who cares? I simply unlock my Stealths from it and attach to the Sting Ray and start planing. Yes on the upper limit the bow open the water and spray it in my ankles, so pheraphs something could done better for this situation, but it's always the time to switch to a planing board; i remember similar problem in some situations with my Wizzard, designed by Peter Thommen, and I've read something like this also about Witchcraft tests.
The fact is that in my experience since about 1996 I've never find anything so beautiful and gliding, neither in long and narow board of that time, I mean 320, 330 and 350 cm with daggerboard, so for us "late" windsurfers Serenity is absolutely new even if is declared not to be new from his own designers, they clearly say it's inspired by Div 2 boards.
About your last statement I'm not a shaper or engineer, but I'm a little bit surprised, but still.. serene on it. On the deck is written designed by Svein Rasmussen, Jim Drake, Per Andersson, Tiesda You. Especially the second one is not the ehm last name in windsurfing (literally the first).
And also the other guys are not so novice, that guy named Svein is involved in board design since a lot, and some ideas he had changed the history of windsurfing.
But I'd like to understand, what are the things in Serenity shape that could be changed or improved? I can't imagine an even faster lightwind board, so understanding where are the problems could be helpful.