Personally, I think Haste’s usefulness caps near ~25% in keys.
In Raid, the faster you can cast, the better to both ramp faster, and get more out of your atonement window.
In dungeon, your atonement window isn’t going to cover everything (currently) and our DoT in Shadowlands is… terrible. So you’re not getting huge returns on dot damage either. So at that point, it’s haste up till you feel you don’t have any problems covering people - and other stats after that.
For talents, I’d drop castigation unless you’re using penance mostly defensively for its heal or are seeing very low Twist uptime (you can check this in details overall). Twist of Fate is generally better any uptime above ~20%. If you’re using penance defensively a lot, then sure it’s getting more value. But looking at your log, it doesn’t look like you are. It also has some anti-synergy with purge, because you want to use it offensively to spread that.
For stats, again I think keep as much haste as you’re comfortable with, but otherwise focus it into verse/crit.
Your trinkets aren’t very good right now. Having at least one good damage trinket is usually great for your DPS. If you CAN you should try and grab a resonant reservoir from the SoFO raid. If you don’t want to raid, next best damage trinket is from upper kara - the lightning orb one - I think called volatile energy orb. You can also grab an Iron Docks Enforcer’s Stun Grenade and use it when you’re about to boon - which will increase damage a ton. As far as healing trinkets go, most the healing trinkets from dungeons are pretty awful - the best ones are probably the spectral feline in sanctum of domination, or the carved ivory keepsake from the same place. Generally should go with a stat stick like Soleah’s in that spot.
Look for a rebooting bit band from workshop, as opposed to the shielding one you have. Rebooting bit band is insane value on discipline, because we generally let people hover a bit below 100% health outside grievous weeks so it overheals way less than on other healers.
For conduits - yours look fine, just need upgrades on em. If you start struggling for mana, can get another potency conduit and add in the attack speed conduit for your mindbender (from shadow).
For getting more damage out - I think the culprit (on top of not having a good damage trinket) is your boon use. From most your logs, it looks like you’re rarely casting ascended nova. Which means you’re getting significantly weaker ascended eruptions, and your damage is lower overall. There’s some dungeons where moving into melee at certain times is terrible, so I’m not faulting you there. But whenever you can, you should be trying to Blast>nova>nova>blast on repeat while boon is up.
As far as extra tips, those tend to be dungeon dependent or surrounding our utility (mostly mind soothe, mind control, mass dispel, shining force and leap of faith). Overall looking at your logs, I’d say find more places to use pain suppression. Usually you can do this by tracking tank CDs and in larger pulls using them when the tank CDs are coming to an end. But I mean if you get through with lower Pain supp use it’s not exactly a problem as much as it’ll be good practice for when your key level gets high enough that you need it.