Butcher's Circus: Martyr Comp
This team is based around the idea of having gigachad carries like the Leper for big damage, Crusader for big stuns (and damage), and Jester for accuracy + Finale pressure. Who's supporting them all? Well, the Martyr of course. The Flagellant's job is nothing more than to keep everyone feeling healthy, take the pressure off of them and redirect it to himself. Having him in the back is actually nice because you have more control over his health, as he's usually not being focused down. You also can't stun him in the back. If he does get pulled, you can always Holy Lance into Dirk Stab to reposition him, if you want. But the Flagellant's doing just fine wherever he's at, really.
I won't detail the other characters in depth since they're more-or-less pretty standard. I give the Leper the Durable Armlet instead of Eagle Eye Talisman because the extra health works nicely with Flag's Redeem, but I think either trinket is good.
For playing the Flag, you HAVE to understand that his job is to enable the carries on his team to do their job, take the pressure off of them. Unless someone's received a meaty crit for a chunk of their HP right away, you're usually acting last with him. If someone's being pressured immediately with damage, drop a Reclaim on them. Worst comes to worst you still have a Crusader for some extra heals in a pinch. Otherwise, if your enemy does a lot of round 1 setup, it doesn't hurt to get some Suffers going to prepare yourself for stress healing and boost your DB resist for the future, or if you think maybe your Jester will get focused you can drop a preemptive Reclaim. Ultimately, you have to pick your Flag actions pretty carefully, and sometimes you'll have to take risks at death's door to get the most value out of him (this is why you have Suffer!)
I run my Flag with Brass Bugle to make him flexible against all types of opponents. Gauntlet of Absolution boosts his support skills just fine against Damage and DoT teams, but against stress? 30 stress healing just isn't enough value. 45 heals back more than the enemy can deal in one move against one target, generally. Your team will afflict eventually against a decent stress team, but this can take a lot of pressure off of someone being focused.