The health in game is 100 units as it has always been. The damage values of the weapons are similar to what they have always been. You are experiencing good hit detection and low latency like we had in MW2 and prior CODs. The terrible hit detection and high latency of BO1, MW3 and BO2 has skewed your expectations of how the game should play.
We COD veterans appreciate this return to the tight responsive gameplay of the good old days. If you want hitmarkers galore and HALO-style, 10 second long gunfights, then stick to those broken games that we abandoned in frustration long ago.
The real Call of Duty is back and not a release too soon.
You are correct in that weapon stats are very similar.
Low latency/good hit detection could also be playing a part. But TTK does seem a lot shorter in some situations and I'm not sure I'd believe it's entirely due to less lag.
I'm wondering if maybe they increased the max damage ranges of the weapons. I haven't found stats that show the range measurements in the same units. Silencers don't take as much of a bite out of range as in past games. Also a lot of the guns seem to have less recoil than in some of the past games. Any of those things would shorten TTK in a lot of situations, all of them combined would shorten it even more often.
Here are some hard numbers comparing BO2 and Ghosts assault rifles. These are max and min damage values for assault rifles. You can see the values are quite similar. You could even argue BO2 had more powerful weapons. The problem is so many of their hits never registered.
BO2 damage values Ghosts damage values (max-min)
MTAR 40-24 SA-805 40-25
Type 25 33-24 FAD 34-25
SWAT-556 40-33 Honey B. 42-20
FAL OSW 55-40 MSBS 55-20
M27 IAR 33-24 SC-2010 35-20
SCAR-H 45-33 AK-12 49-25
SMR 59-49 Rem. R5 49-20
M8A1 35-24 ARX 43-17