On my Blair i play the 7s coldown ult build hit for 6 million or you play a full DPS build for hit 8 millions on boss. The build on the video are a mixe a this too build soo I don't know, with 7s CDR build when the boss fall I can hit 5 ult for 5million and after I have no mana so i use my 2 and i can have a third one soo 15 million dps in 21s and i shoot with greg betweens my ult and with the full power after you ult use your 3 because he it's very hard when the boss fall 🎉
The critical resistance is irrelevant. Look at the other half of the mod. He does it to squeeze in more fire skill power. If you look at the numbers, the build with fire synctium does more damage.