SPvP Viability
Unless you are competing for money, guardian bunker and guardian meditation dps will work sufficiently for general play.
Medi guard is used competitively, but it’s usefulness is debatable.
Medi guard does very well against other DPS builds and is arguably best at 1v1 against DPS builds. And it counters thief. Depending on the variant, medi guard can also bring decent group utility. But in larger group fights, medi can be focused down easily, and it lacks the map mobility of a thief.
While Med guardian has better self sustain then some other berserker specs it does not have ready access to cripples or chill on a low CD.
So while it can stand toe to toe with melee enemies it will often die to any skilled opponent smart enough to kite.
As for bunker guardian.
It has very good support for a group but unless it has allies around it’s self sustain is nowhere near as good as it could be. It also has extremely low damage potential & little if any crowd control abilities.
This makes support guardian sub par to support Ele & engineer. Especially when so many classes can simply use celestial builds & bring a medium of defense & offense thus eliminating the need for a bunker guardian.
There have been numerous discussions on both and how they could be improved/fixed/brought back into meta but unless Arena.net decides to do something I would expect to see less & less guardians in the top tiers.