I’ve written a couple articles for Blizzard Watch on ranking for Krosus – one for ranged and one coming soon for melee.
To squeeze out that extra DPS, you’ll want to pick gear specifically for that fight. For every 1% you increase your DPS, you can expect to move up 1 – 2 % in the rankings.
One extreme example is for dual wielders: Krosus has a bug (at least I assume it is), where you can’t miss on him. Normally when you are forced to hit a boss from the front, the boss mechanics that make him dodge or block your hits is turned off. But you can still miss in those cases. However, it looks like the ability to miss was also turned off, meaning you never miss a single hit on him.
In a few quick tests on some dual-wielders, I found most of them get a 2-4% increase in damage when gearing specifically for this bug, compared to gearing for a regular version where you still have a chance to miss.
So ‘regular’ gear advice isn’t going to optimize for doing the most damage under the specific Krosus scenario. So I have an option for you to gear specifically for this.