Hello there fellow blood DK
You want to go with Evergaze from Imperator Margok (yes it is better than trinket off hanz&franz even at lower ilvl) & Blast Furnace trinket. The mastery trinket is nice from Hanz&Franz but not optimal in my opinion.
The on use trinkets are utter crap compared to to trinkets with procs, and are better in the long term of things in any fight.
Here are some logs from Mythic Flamebender & Mythic Kromog (server 1st blood dk rank in both)
https://www.warcraftlogs.com/reports...uras&source=18 - flamebender - blastfurnace trinket proc 4 times in a 5:11min fight and evergaze proc 8 times
https://www.warcraftlogs.com/reports...auras&source=5 - kromog - blastfurnace trinket proc 10 times in a 7:50min fight and evergaze trinket proc 9 times