I never stepped my foot into Mythic, but I'm gonna point out some stuff that goes with Gruul in general. Gruul is a fight that depends on either u get or don't get petrified. I checked the logs from the fight where u survived for 4:20, u had only 8 Storm Bolt casts and not to mention u were using AM. A normal 4 minutes fight with no AM should allow u to use 9 Storm Bolts. The fight was 260 seconds. BT usually has around 4 seconds and less CD, so 260 / 4 = 65 BT casts, u had 58. I know it's not a big difference but these 7 casts could've helped u get ur Enrage uptime better. There was a time where I saw u had Sudden Death proc for like 5 seconds, but u prioritized BT, WS and RB over it.
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The secret of success on aoe fights like Darmac is to communicate with all the warriors u have in ur group. Like for example, when I first got into heroic mode, our group had like 4 dps warriors. If all of us 4 used BS on every pack, none of us would have good dps cuz the pack would die in less than 1 second. Now I have no idea how his BS off hand has 2M more dmg than ur main hand BS dmg. U have Siegebreaker talent, this is a useless talent for this fight if u wanna do good dps. If u go AM, u still won't have BS/DR for every pack, so try going Ravager. U have to know whenever every pack is gonna be spawned and plan ur cds ahead. If u have a program like Fraps/Mirillis Action or any other program that can film, do it. Use /sw ingame and turn it on like 2-3 seconds before the boss is pulled, and then check ur video fight. Write down all the times that the packs will be spawned and then use /sw again on ur next run, u will be planning everything ahead. Same goes with Thogar.
Now a good way this fight and Thogar is to just charge and use ur normal skills, don't use any cds. 5 seconds before the pack is spawned, u use Reck and ur trinket, make sure u r Enraged, use DBS and do a Heroic Leap into the pack followed by a BS. It's always good to use BS after Reck by 4-6 seconds cuz of the t17 4p.
P.S: Ur first BS was un-Enraged.
Now Oregorger: Both of u have an extremely low Enrage uptime. U didn't use Glyph of Rude Interruption, 6% dmg is really amazing. He interrupted the boss 8 items (same as u did) but he had the glyph and u didn't. U guys have to always be checking ur group's dps and what ur raid is cappable of. This boss took u 6:11 so if both of u had gone with AM, u both could've used 1 additional Reck. U saved ur Reck to the end, he used it in the middle hoping he could get 1 at the end. U used ur potion a couple of seconds before the boss died.
His starter was a lot better than yours, u charged in and didn't even use BT. U just went in using Siegebreaker + Execute and then another SD procced so u used Execute again. U can never do ur attacks un-Enraged, it's crucial on one's dps. His terrible mistake was to go Bloodbath for this fight (cuz he had Scabbard), if u wanna go Siegebreaker, Bloodbath or Avatar depend on ur trinket (Vial = Bloodbath and Scabbard = Avatar).
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I'm not good with Blackhand and I never did any boss on Mythic. But well, the more aoers u have in ur group, the less dps they will do.