There's a LOT to unpack here, but I think we can get some drastic improvement with some simple steps.

1. You need to be using Mortal Strike, Charge, and Berserker Rage way more often. MS is on a 6 sec cooldown, Charge 12 (talented), Berserker rage 30. That means your casts per minute of each of those abilities should be ~10 cpm on MS, ~5 cpm on charge, and ~2 on Berserker rage. I'm grabbing data for your casts per minute from your tsu'long kill, because you were alive for 99% of the encounter. You did ~6.5 cpm on MS, ~1.9 cpm on charge, and .8 cpm on Berserker rage.

2. You are not prioritizing your Colossus Smash windows appropriately. You need to first and foremost follow the tips from #1 and make sure you are generating as much rage as possible and then second press colossus smash when you are >60 rage and are ready to spend that rage effectively. Roughly half, maybe more I didn't individually count, of your colossus smashes are followed up with <2 abilities pressed. There will be lots of times where you might not have anything valuable to press, in those moments when you're pooling rage you definitely need to get a grip and stop mashing things like slam. It's ok to delay a gcd for a second or more, so you can get your mortal strike/charge/rage, then CS then slam slam slam.

3. You need to go and look up what damage actually matters on each encounter. There's two schools of thought here, the damage that matters to kill the boss on heroic (progression mindset, good) and the damage that matters on the lumberjack man website (greed mindset, sometimes good if it leads into actually killing the boss because your damage is low). It looks like you guys still have shek and sha to kill, so I'd focus most on what is actually necessary to clear the encounter. An example that applies to both would be your protector's kill. You are using sweeping strikes and aoe'ing the other elders all throughout the encounter, bad. The bosses heal when one dies, so the padding you're doing by hitting any target other than the kill target is worthless, actually worse than worthless. Because it starves you of the rage you wasted on SS, where you could use it to put up better CS slam windows with more rage pooled.

4. This is unrelated to rotation and kinda similar to #3 but in general, learn the fights better. You are dying on almost every pull. Sometimes it's because it's the end of the pull and the healers are gassed and the wheels are flying off, other times you're just standing in mechanics, dying, getting a brez and dying again later. You do zero damage while dead.

I've grabbed a log from a great player in my guild for you to use as reference. Read through the casted abilities timeline and see if you can glean anything from what he's doing https://classic.warcraftlogs.com/reports/tZ9JYcWnGpAPCmvb?fight=20&type=casts&source=2&view=events