Ok, so a quick rundown of the basics:
*DMG Math recommends the following for a level 22 soldier (thanks to Asmor):
HP: 1055; Bloodied: 527
AC: 38 Fortitude: 35 Reflex: 34 Will: 34
Increase 3 of the 4 defenses (including AC) by +2 each.
--Stats for an elder red dragon, level 22 solo from MM:
HP 1050; Bloodied 525
AC 40; Fortitude 40, Reflex 37, Will 34
only a small diff in HP, defenses a bit higher except for AC which could theoretically be spot on.
*Level 21:
HP: 1010; Bloodied: 505
AC: 37 Fortitude: 34 Reflex: 33 Will: 33
Increase 3 of the 4 defenses (including AC) by +2 each.
--Adamantine dragon from newest preview
HP 796; Bloodied 398
AC 37; Fortitude 36, Reflex 33, Will 32
HP is _definitely_ low, only fortitude seems to be within the recommended math. for reference, HP*4 would have been even 808, so this creature falls low even on that HP scale. Now let's look at damage
*Red:
+Level 21 recomends:
Damage Low | Medium | High
At-will 2d6+8 | 3d6+8 | 4d6+8
+Claw (Standard, at-will)
Reach 3; +29 vs Armor Class; 2d10+9 damage.
+can do 2 claw attacks
+total is roughly 4d10+18, well above a single High damage point, but well below 5 times that.
*Adamantine:
Damage Low | Medium | High
At-will 2d6+7 | 3d6+8 | 3d8+7
+Claw (standard; at-will)
Reach 2; +26 vs. Reflex; 1d12 + 8 damage.
+Bite (standard; at-will)
Reach 2; +26 vs. Reflex; 2d8 + 8 damage, and ongoing 10 damage (save ends).
+Can do 4 claw attacks, plus 1 bite
+total of 4d12 + 2d8 + 40, 5 times the low, med, and high would be 10d6+35, 15d6+40, and 15d8+35 respectively, if 1d12 is comparable to 2d6, we could estimate this at will attack being somewhere above 5 times the low end.
while it's unrelated to damage, the reach on these is only 2 for an elder (normally is 3). Red has a difference of +3 to hit for only 1 level difference, but as others have pointed out, attacks AC rather than reflex. There are plenty of posts to point out that the difference between AC and reflex is often much more than 3 for anyone with a decent ref.
The dragons appear to have comparably sized breath weapons, both recharging on a 5 or 6. both doing 3d12 + some coefficient. Of course, the adamantine dragon also gets a rider effect of 15 thunder damage on the next turn. Besides the raw damage output, this is an interesting way to make the breath weapon change the way a turn unfolds over more than 1 turn.
Both dragons appear to have comparable"Frightful presence" moves as well.
All told it definitely appears to reflect a change in methodology of solos. The main nagging issue is that the difference between reach 2 and reach 3 DOES appear to be at least partly responsible for the damage descrepency. In all fairness, having extra range SHOULD equate to the red dragon doing less damage. How much though, i couldn't say. The fact that the red's basic at-will is barely beating out the high damage for a SINGLE creature at that level suggests he'd need a bit more, even being a soldier. obviously bringing all that damage to bear on a single player in a single round is part of the reason they can't have a flat x5 multiplier, but things like the adamantine's requirement of the bite hitting someone else seem to hint at some design space that could ameliorate this.
For now I'd say the general indication is that you could safely trade 1/5th a MM or Draconomicon dragon's HP for an extra claw attack and some kind of rider, damage or maybe an AC penalty, to the breath weapon and come out with something similar to this new style of dragon. There is a saying in design for Magic: the gathering that dragons are allowed to be strictly better for their casting cost simply because they're dragons and are iconic. It's ok for dragons to be ahead of the curve for a given level range because you expect dragons to be powerful. Of course, you also expect to be able to BEAT the dragon, so tread lightly.