You will get it, keep it up! The ice stage boss always ends up being where a no death run is potentially spoiled for me, seem to get unlucky with burst at times.
Stage 7 make sure to block when those lurcher's shoot our their triple flame wave thing. They are almost impossible to dodge roll away from in my experience. Also the mini boss Dragon Knight woman, make sure you kiting her around the room a little bit, so that when she drops her standard, she will start chasing you and move out from the middle of it. Easy to get one shot if she is standing in the middle of her banner and chains you into it.
On stage 8, this is probably common knowledge but I literally never knew this for the longest time... when you are upstairs during the boss fight, there is that floating rock thing you can hide behind to avoid getting knocked off... lol
Also helpful on last boss when upstairs, when the last crystal gets low, throw all your DoT's / AoE's down and jump down before it dies, so that your effects will kill it and you won't get knocked back into the lava.
And yeah on that last part just focus on the mechanics. Grab gold ghosts, kill daedroths (make sure you circle strafe these to avoid get soaked with their flamethrower), kill summoners, interrupt boss.
At the end of the last stage before the final boss spawns, if you don't have ultimate ready, just use light attacks on the enemy ogrim to build up to 100% so you have it ready for the last boss. With enough burst you can just immediately skip phase 1 and he will go upstairs. (actually with enough DPS you can literally kill him outright, involves saving a golden ghost synergy and using it at the start of the boss fight to stun him... but that is Maelstorm level 400 classwork)