So surely by now there are 1000+ guides out there, most are probably better than mine.
However they STILL don't mention the teleport timers and the mechanics before the Templar teleports, making this a serious PITA for people trying to run it with LFG groups.
Here's a 5 minute video mentioning the entire thing along with failed runs, successful one and some weapon recommendations as well. EDIT : Apparently previous link was wrong.
My first run we failed for about 2 hours straight until we understood the very simple timer mechanic for the Templar.
The Templar Teleport Mechanic
Pick up relic.
Make sure to kill 4 oracles so that everyone has enough time to charge supers and get synths.
Break shield using relic super.
Watch teleport circle BUT DO NOT GET IN.
Start counting down from 10. At about 2 or 3 step into the circle and use the relic grenade button to shield self.
Shield as required, the teleport point will change.
Rinse and repeat.
This way everyone else stays safe but the relic carrier and maybe one more person if you choose to split teleport block responsibilities. Both of which have very safe spots on the map and the relic to block themselves.
The templar teleports at the END of the 10 seconds not the beginning nor the middle.
There's no need to rush the teleport point to stop him from doing so. This method works for people with all random kinds of stat builds, high dis low dis whatever.
I know this is extremely basic but it just seems that most people seem to panic too much or just not understand the timer before the Templar teleports. Once you get this down you can keep going indefinitely to lower his health.
I have mentioned some weapon recommendations in the video as well.
I hope this helps the tonnes of people that are having a hard time running this challenge.