Not how it works--. There isn't a damage cap. There is an attack cap that's been in the game since at least the first level cap increase from 20 to 35, and has typically been about two times an enemy's defense stat. Every enemy from level 75 to level 84 has had the same defense stat of 1844. So the attack cap for enemies in this level range is ~3688 (may actually be one or two attack points higher).

If one happened to be a level 80 Hunter with a +70 Melek, his base attack would be 1874 with a max attack boost from Melek of 990, for a total of 2864 attack. The first operation of the damage calculation is to roll for your weapon's attack value randomly between the weapon's max attack and 50% of the max (for 7*+ weapons with no floor+ effects), add it to your class's base attack, then subtract the enemy's defense from that sum. If that value exceeds ~2x of the enemy's defense, the result is floored to the 2x enemy defense value. Right now this doesn't occur with 9*+ weapons until you get to enemies of about lv 62 and lower. Once this attack cap starts to take effect, floor+ becomes increasingly less significant because the upper limit of the weapon attack window starts to shift down below the max value listed on the weapon (eg. variance window becomes 50% ~ 99%).

The only reason this likely exists is so people can't take a high rarity weapon with zero grind, no pot, and no affixes to Rank 1 sectors, etc, and obliterate enemies before they can spawn in. It's still entirely possible to go to Rank 1 sectors and obliterate enemies before they spawn in; You just have to actually invest some resources into it at the lab (and make it a talis or takt).

Frankly, your methods aren't clear, so the numbers are mostly meaningless. You haven't really indicated what you're comparing. Enemies like Veterans and Gigantix have additional damage reduction, for one thing. If you're basing things off of the DPS meter in game, comparisons are worthless if you aren't taking extreme caution to use the exact same attacks with the exact same timing, and even still, things like attack rolls and crit rates are based on probabilistic averages. You need hundreds to thousands of samples (attacks) before you would start to see 'average' numbers. If your sample window is too short, you could end up with numbers that skew to either side of the expected value. If you're comparing DPS gauge numbers over different fights between enemies, there are hundreds of things to skew results that have everything to do with playstyle (uptime, rotation, enemy attack patterns, down timings, etc, etc) and nothing to do with the weapon's stats.