For Dark Souls I kept a running journal for the first month or so after release; including wondrous death counts and I think it's an interesting exercise predicting how many you'll have and where they'll come from. I won't have an endless supply of time this time around but I'll try to do the same thing for Dark Souls 2. For me the most deaths I've ever had in an RPG was Vagrant Story at around 130, 25 or so of those being to the last boss; I was 13-14 at the time but that's still my personal threshold for declaring a game as the "hardest ever."
And here we go:
Falling - 25
Generic Enemies - 10
Less Generic Enemies - 10
Traps - 5
Gwyn/Artorias/Manus 2.0 - 10
Kalameet 2.0 - 10
Puzzle Bosses - 5
Other Bosses - 5
I come up with 80 here, my general assumption is around 75 as I expect Dark Souls 2 to be roughly as hard as the original; but who knows they could throw in a curve ball. I don't include PvP in the prediction since that's really hard to predict and even harder to predict at launch/will vary tremendously from person to person. It goes without saying that this is a blind run with a "blind" build.
With Gwyn/Arty/Manus I expect there to be 2-3 bosses of that esteemed caliber and to die around 3-4 times to each; most other bosses aren't going to be a huge deal aside from the potential for Kalameet. The biggest curveball I could anticipate is a boss that is also a puzzle; i.e. you do the puzzle and then you fight the boss and both parts of this process are harrowing; and that might be like 10 deaths by itself. There are also things like the Capra Demon and the Butterfly that could throw things askew.
For Traps I don't include those that involve falling to your death, since that's obviously another victory for Gravity, by far the most prolific murderer in the souls series. I also include things like the Hydra or the Bridge Dragons, because they effectively function as traps.
If there does happen to be a Four Kings I don't anticipate it being particularly difficult on the first playthrough, though on NG+ some will undoubtedly get screwed because of how you built your character. Here's to hoping there's no gear-checks.