Low Damage F1 Condi

I made the standard Condi Firebrand build with full exotic vipers and I get ~19kdps on golem with F1. If I drop F1 from my rotation, I do ~25kdps. My condi duration is about 95%. I know F1 excels against multiple targets where you can get the reset, but I've seen this build do tons of damage with F1 in the rotation on golem from other players, and all the guides say F1 is your main source of damage. So I feel like I must be doing something wrong.

A lot of your damage comes from f1 5 skill, which makes your party do burn damage on attacks that attributes to yourself no?

That said, 4 then 1 spam should be a decent amount of burn stacks too no?