You need to ensure that you run Eradication and Roaring Blaze talents f or the 10% and 25% Incinerate buffs respectively. Then use and on-use trinket before the incinerates.
Deci bolt is a double edged sword because its not your strongest execute option yet strongly pushes you to use it when the target is low health. It ends up that you use it on a low hp target to get the buff, but they’re already healed to full and if you’re lucky to get any of three incinerates off before they are purged off, one 20k damage is actually laughable in a meta where a completely random Execute proc for a warrior can hit 32k crit.