I’m on a solo trip to the jungle with Dapper-Harvey right now. His fine clothes, alongside this card, has gotten us out of many a tight spot with inquisitive Brood of Yigs. Together with Crafty it gets even better.

To synthesize other reviews (and then add to them), I think we can say this card is "not great" in general :)

It might be good if you're playing in Hard/Expert (to avoid the Chaos bag) or a Curse deck. But it might be really bad otherwise (even 2 curse tokens can destroy an important skill test at the wort moment).

BUT,
no other review considered this card when you Investigate on a 0-shroud location ! Then it becomes one of the best investigating card : 2 clues for the cost of only 1 action (and synergies in your deck).

Cards like Arcane Insight or even Vantage Point might completely negates the cost of Stirring Up Trouble.

So you could easily take 2 clues from a 2-shroud location (or reduce the price to investigate a 4-5-shroud location but not ideal).

This card is fantastic and is basically a free emergency cache with streetwise. Boost streetwise on a test and commit this, succeed by 3 and basically carry over the streetwise boost to your next skill test. It goes a long way for economy in a class that can be very expensive. Behind easy mark and three aces, this is probably the next upgrade I shoot for in a standard rogue deck.

I’m curious to understand how this interacts with Brother Xavier or True Grit in terms of allocated damage from another investigator.

By my reading of the damage rule, damage is dealt to the other investigator, then assigned to an asset, then applied to the relevant asset or investigator.

The rules don’t use the word “take” at all, so I would assume that the owner of the asset could play Lesson Learned even if not actively engaged with the attacking enemy.

Guardians thematically stands guard at the same location as the Seekers to help with spawned enemies, but that is not enough as you still have to spend Engage action to grab it if you are not the one that draws the enemy. Guardian also loves to dispose the enemy quick before its first Enemy Phase arrives, so 3 actions are not to be wasted.

"Until the end of phase" split this card to 2 use cases : Investigation Phase or Enemy Phase.

For Investigation Phase usage, this card buff all your other friends at Mythos Phase with something that feels like this very expensive Ward of Protection (5) or Disc of Itzamna (3) that could kill an enemy Mythos draw. They can go first in turn before the fighters, continue using Investigate/any business they want to do, provoking AoO, then the enemy is instantly forwarded to the Guardian fighter at good deal of probably 1 health each. Guardians love 0 horror spill (including the guardian dog). Guardian go the last, then use full 3 actions to take it out. Not only you save actions, you also gain back turn order flexibility.

Enemy Phase usage is rarer. You can defend against incoming Hunter enemy, and is a play of Prey criteria :

• If Hunter but no Prey : No need for this card if you decided to stay, as you can already select engagement target.
• If Hunter and has Prey that is not you : Stand guard and let it walk in. It engages with Prey instead of you, then play this card. Though, without Get Behind Me, Guardian can instead walk forward to it and take free engagement instead of standing guard and fight (i.e. standing in its way). Downside of doing that is you can no longer receive commits from your Seeker friend and also lose an action to walk. Get Behind Me still has good value opting to stand guard strategy against Prey enemy.
• If Hunter and has Prey Only that is not you : It is almost same situation as Prey but according to the rule the Guardian no longer able to walk forward and take free engagement, you must additionally waste Engage action. Resulting in 2 wasted actions before the fight, which you may not be able to take it out. In this case, Get Behind Me can save you that 1 Engage action in addition to all other benefits of just standing ground.