Themed tank dps am I on the right track?

Well, one issue is that Firebreath won't proc with your toggle/form or EU- though I guess that's not a huge deal if you're only tapping it against scattered mobs to tag them w/ Challenge.

Anyways, if this is meant to be an SB build, then you prob do want Reaper's Caress for the bleed buildup and for the easy access to Shredded. You'll be generating a lot of threat when playing as a dps too, but I guess you can work around that. I may also keep Dragons' Bite for Rush's extra energy, and get Physical Peak in Str PSS. Could also use Steadfast as the EU if you're already gearing for Dex. Here's one way to edit it:

Muramasa bladed tank - Freeform (Any / Multiple)
v3.41:33

Super Stats
Level 6: Strength (Primary)
Level 10: Dexterity (Secondary)
Level 15: Constitution (Secondary)

Talents
Level 1: The Savage (Str: 10, Dex: 8, Con: 10, Rec: 10)
Level 6: Enduring (Con: 8)
Level 9: Mighty (Str: 8)
Level 12: Agile (Dex: 8)
Level 15: Martial Focus (Str: 5, Dex: 5)
Level 18: Acrobat (Dex: 5, Con: 5)
Level 21: Quick Recovery (Con: 5, Rec: 5)

Powers
Level 1: Throw Fire
Level 1: Reaper's Caress (Rank 2, Cleaving Strikes, Challenge!)
Level 6: Steadfast
Level 8: Defiance (Rank 2, Rank 3)
Level 11: Form of the Swordsman
Level 14: Crimson Bloom (Serrated Edges, Challenge!)
Level 17: Endorphin Rush (Rank 2, Rank 3)
Level 20: Reaper's Embrace (Rank 2, Rank 3)
Level 23: Fire Breath (Challenge!)
Level 26: Resurgence (Rank 2)
Level 29: Dragon's Bite (Dragon Rush)
Level 32: Telekinetic Shield (Rank 2, Rank 3)
Level 35: Way of the Warrior (Rank 2, Rank 3)
Level 38: Vorpal Blade
Adv. Points: 36/36

Travel Powers
Level 6: Acrobatics (Rank 2, Rank 3)
Level 35: Ninja Vanish

Specializations
Strength: Swole (2/3)
Strength: Physical Peak (3/3)
Strength: Brutality (2/2)
Strength: Juggernaut (3/3)
Vindicator: Aggressive Stance (2/2)
Vindicator: Merciless (3/3)
Vindicator: Focused Strikes (3/3)
Vindicator: Mass Destruction (2/3)
Warden: Fortified Gear (3/3)
Warden: Slaughter (3/3)
Warden: Ruthless (2/2)
Warden: Elusive (2/2)
Mastery: Strength Mastery (1/1)

Stuck ERush in there for a cheap, decent self-heal for a tank, though you could also take Conviction there.

Yea, but you mine as well use the basic combo for bleeds and shredded, since it's not constrained by a cd or charge time and can be a basic melee attack to use when you're not blocking or don't have bleeds fully stacked yet. That's not to say that Tornado Slash is bad- it just fills a kinda different niche.

Maybe what you could do is keep Challenge off of DB and give it Rush + R2 (you'd have to remove a rank from something else in my build), and then it can be your main attack when dps'ing (Vorpal Blade can put up Bleeds, if you want to not use RCaress then, and I didn't put challenge on REmbrace so you could still use that). It won't be ideal for dps, but it's a dual-passive build anyways so that's somewhat of a given, and I assume you value the performance of the tanking part a bit more than the dps part.

Yea, I considered FotT as well. Esp if he wants to use Firebreath more than that's the better choice- it's a bit more rng-based, but it could work too.