How do I calculate DPS vs. another player?

I use the OSRS Wiki's DPS calculator a lot but I have always wondered how to use it to calculate DPS vs. another player (or if that's even possible).

Here's a custom loadout with basic range gear from LMS. Is it possible for me to use the Custom Monster enemy to mirror the stats of a real player in LMS (I'm assuming that, if they're praying, I just reduce DPS by 40%)?

If that isn't possible, how do I calculate this sort of thing? I have also wondered this in the context of freeze chance. I understand that these OSRS Wiki articles detail how to calculate DPS:

• Damage per second/Melee, detailing melee damage output calculation
• Damage per second/Ranged, detailing Ranged damage output calculation
• Damage per second/Magic, detailing Magic damage output calculation

But how do I factor in someone's defense level, what they're praying (offensive & defensive), gear switches, etc.?