Dungeon/Raid Support/Tank?
Tanking doesn’t mean you stack up toughness and healing power and facetank. Tanking means you slap on one toughness trinket and some defensive traits/weapons/utilities to hold aggro so most “tanks” still use almost full zerk with one knight trinket or something.
Yes there is now tank and healer in raid and raid alone. That said, they are really not like a normal holy trinity.
There is several ways to get the job done. For exemple the healer. Two main strategy exist. You get the support Tempest that pretty much give 40% protection to the party, and boons to keep everybody up. Or you have the druid which have more burst heal for specific moment when some people are in hard place.
You can also have profession like Guardian or Herald put out perma protection to limit the healer’s job easy. Some even only bring Beserker Healer because they don’t need that much heals.
The tank, it’s even more different that the Holy Trinity counterpart. The tank job is to keep agro and survive. But for that, he usually don’t need much tankyness. For exemple, a Necro or a Mesmer can tank in a full zerker armor with only some pieces of knight for just enough toughness to keep agro. Tank also usually need to bring 1 more thing to the raid. Some bring buffs, like the ChronoTank. Other bring dps like the Reaper or the BurnZerker tank. Other bring protection and CC like the Guardian Tank.
Here one exemple of tank build for guardian. Narc also have a more offensive version, but it might be hard to play when you are not experienced in raid and don’t have a good group so.
If celestial is too expansive for you, you can make a mix of stats to match around the same stats as a full celestial for a smaller price.
There is a lot of different option. But IMO Writ of Persistance and Hammer are a must for tank guardian. Not that you can’t tank without it, just that it’s this little something else that Guardian can bring. Protection on your melee group will make sure they down less and dps more. Make the life of your healer easier, etc.