Cooldown cap is 60% -- Let's turn this into a list of limits/caps.

[Vox]

After a lot of searching, I was unable to actually find anywhere that listed this fact, so I ended up figuring it out myself. You can tell when the cap is hit because the cooldown number on your skills turns red.

Besides sharing this information, I thought it'd be useful to share another caps and limits in the game. So, feel free to add some. As I go about min/maxing my Arcane Mechanic, I will continue to add information too.

[Psojed]

Well there are only three limits that I know of, Critical damage bonus %, should be at 450% unless that changed. Critical hit % should be 50 % and Cooldown Reduction % which you already know.
The first two can be transcended by some skill bonuses that say so. I haven't played VH2 for a while, but I'm pretty sure it's the same in all 3 games.

[Geotarrr]

There's another limit/cap, concerning the character-classes that use the attack speed statistics (like Hunter):

The attack speed with skill, which has no specific cooldown pointed, is limited by the global cooldown statistics (which is 0.5 seconds).

In other words if your attack speed bonuses, applied to the base attack speed of your current weapon, would result in value lower than the global cooldown, you will still attack with this skill with speed, limited to the global cooldown.

[Psojed]

True, some skills have a set cooldown, so even if you didn't reach the 60% cooldown reduction cap yet you might reach the cap on skill cooldowns..

But you mention attack speed, which puzzles me. Weapons with aspeed 1.00 are slower than weapons with aspeed 1.60. Also the game displays your attack speed as a value, so bonuses actually increase the value - your attack speed can be 2.00 or higher. The statistics window does not display a red number at this speed. This can be tested with Hunter's basic attack.

If attack speed is limited the same way the global cooldown is, it would mean that 2.00 speed should be your cap (as in 2 attacks per second, which corresponds with 0.5 cooldown). However I do not know how attack speed translates into attacks per second. Maybe you can bring more insight into this?

[datguy13]

If I remember right, 2.68 is the hard cap for Attack speed, which translates to 3 basic attacks per second. As Geotarr notes, though, the Global cooldown affects all skills with a 0.5 second minimum cooldown, so the only attacks which can truly benefit from the attack speed hard cap are basic swings.

[Geotarrr]

Yes, I've meant the attack skills on characters, using attack speed, other than the basic attack, i.e. skills like Explosive Shot, Icicle Shot, Scattershot etc.

So if you want to consistently use given skill, it's better to not boost your attack speed over 2 (0.5 seconds).

And datguy13 mentioned one another limit/cap - the attack speed with basic attack.

I don't know of defense-based limits/caps. Although things like resistances, defense and dodge are naturally limited through the diminishing returns mechanism.

[Vox]

This is all some very good information. I've been playing Arcane Mechanic mostly so I'm not really up on some of the other class mechanics.

Something else I thought would be useful was the highest stat values for level 60 rare gear, to know which ones to use for runecrafting. I'll list the highest ones I currently have:

Boots: Defense 2038, Poison Resist 221 (Combo here as I know Poison Resist can go higher)
Belt: Crowd Control Resist 469
Chargerpack: Base Weapon Damage Increase 39%
Ring: All Attributes 29
Chest: Defense 2628
Trophy: All Resistances 273
Head: Crowd Control Resist 465
Discharger: Damage 104-117 with -16% Cooldown (I have seen 20% cooldown but not as high damage)
Amulet: Spellpower 189

I should note some of the defense values may be affected by the enchants but that's hard to separate. I'm not sure how to get the "true" value.

Other class specific high values would be useful to know as well (as well as any others that trump these). In particular I think it would be useful to try and find the highs for weapon values. I actually have a green Discharger with 132-139 damage and I haven't seen a rare come close to that.

[Psojed]

Thanks for the useful information. I used the basic attack back in VH1 a good deal, but I didn't try to reach the speed cap.

Defense takes the item's base Defense, then it adds any + Defense you might have from bonuses, then it boosts the combined Defense on that item by the amount of % Defense bonus you might have. Essences work too.

For items and their values, you can just check this handy item database: http://tidbi.ru/VHII/eng/index.html
while not perfect, it will give you some insight into possible items.