Hey DJ, Not sure which encounter you were asking about but your link was to a 2:31 wipe on Gorefiend as Destro - pretty tough to analyze. But I notice you had a pet out - not playing GoSac/CR? Also, with the heirloom trinket, I wouldn't expect your DPS to really show up until you got lucky during Feast anyway.
Since you were talking about DoTs though I imagine you were asking about Affliction on High Council? You're right, your DoT uptimes were good. I think as a group TW was cast at a pretty inopportune time and you didn't line your 2nd potion and Doomguard up with it. You'd see better results if it was cast on pull and you used 2 charges of Dark Soul back-to-back with it. You also let Haunting Spirits drop off for a good chunk of time. I think it was probably due to not having shards because you used Soul Swap in your opener. To this day I still hard-cast those DoTs on the opener UNLESS I pull the 'extra' shard by timing Soulburn properly before pull (~22s). It's also a good idea to hold off on Dark Soul on pull until all your DoTs are up. But ultimately, the crazy good results from Affliction locks on this fight are usually a combination of BL on pull, getting the Enrage buff and a short encounter. Some players like to use GoSup with an Imp on that fight, you can see if it gets you a better result.