While the Champion is perhaps the most direct point of comparison and has yet to be remastered, I question the assumption that the class is going to be majorly rebalanced there too. To my knowledge, there is no developer commentary or player consensus indicating that the Champion is in need of balance changes, and the main criticism of the class is that their causes are too restrictive by being dependent on a specific alignment, with evil champions being somewhat under-supported compared to good champions.
In general, the point of the remaster as I understand it is not to set a new standard of balance -- the classes we've seen in PC1 are still in the "balanced" territory we were familiar with before the remaster, and those that received buffs only got them because they were weak (and I still do think the Witch is on the weaker side of balanced, though much better than before). Thus, we still have a solid benchmark of balance even now to measure the Guardian, and unlike the Animist playtest, there are no upcoming changes to the mechanics the Guardian revolves around that could skew our perceptions, at least none to my knowledge. If the Guardian feels weak now, it's likely because they are.