Despite being a weaker DD class this patch, Templar does bring a nice buff to the group through one of its class mastery passives.
Class Mastery
Bright Harbinger grants you 600 weapon and spell dmg and the group 300 for 20 secs whenever you use a Dawn's Wrath ability (so all the time).
Judgement's Brand works with the Burning Light passive (dealing damage) to also increase your damage done with Templar abilities by 1400 for 3.1 secs (whatever this number means I don't know). Burning Light activates fairly regularly so this should be up most of the time.
Sets
The class set Aetheric Lancer has been buffed so works very well on Templar now. It activates on activating Burning Light twice and spawns an area near you that increases weapons and spell dmg and also synergizes with Aedric Spear abilities. The problem is that the area can spawn in awkward places so moving around slightly to place the area in an optimal place can be necessary sometimes. The other set Wrathsun was also buffed but takes too long to gather stacks and hurts sustain.
Sul-Xan goes on the body for add pulls so Aetheric Lancer can go on front bar.
However to make the most of Aetheric Lancer during bosses, it is recommended to go on the body with Null Arca on the front bar. I appreciate that the daggers are incredibly elusive so the other way around works fine as well.
I've recommended Warmask for bosses but if this doesn't work well e.g. the dragon still has the mark on when it flies off and you can't damage the atros as well, replace it with Mora's Whispers demonstrated in the add pulls setup.
I've included another set up using the Shattered Paths Signet with no ults, since Templar doesn't have very good class ults.
Skills
Biting Jabs is your trusty class spammable with a bit of aoe sprinkled in. Used when none of your dots or cooldowns need to be refreshed.
Whirling Blades can be slotted in add pulls instead of Caltrops and used when adds are at low health (<28%).
Power of the Light should be kept up and refreshed once it's ended. Use ults during its duration to add to the damage it does.
Radiant Glory is recommended but Oppression can be used if it can be sustained. Start using this at 28% health.
Stampede, Vampire's Bane, Barbed Trap and Solar Barrage should be refreshed when they end as they provide vital buffs to the build (extra direct damage, crit chance, crit damage and damage done respectively).
Surprisingly, Onslaught from the two handed has been recommended to use on Templar builds this patch. Provides extra pen and crit chance for 8 secs. The destro ult can be used for add pulls which is a solid option.
For the Shattered Paths build, I've placed Carve on the back bar for a long lasting strong bleed dot.