Got around to a lvl 12 version. Thief variant still beats out rogue version (by about 0.4 DPR).
Some assumptions:
-Your target is only adjacent to you.
-At 100g a pop and a minor action, you can afford to apply a Frozen Whetstone to the Bloodiron Dagger every combat at the start.
-Assuming frost vulnerability from the start is the norm here, so I went ahead and did the same. If you miss your target or attack a new one, subtract 4.75 from the expected damage. I should note that is a much more accurate real world value, since you will rarely need to attack the same monster more than once.
-I went ahead and rolled the bonus crit damage from Bloodiron into the base crit math (6d10 once instead of two iterations of 3d10). Same result, unless the bonus crit damage on the next turn still counts as having the cold keyword (since the original attack does). I don't believe it does, but if anyone knows otherwise I will adjust the math.
-The random +1.8 on the Riposte Strike crit math is from Acrobat's Trick (2*0.9).
-For clarity, the attack sequence is Riposte Strike (crit > Free MBA) [ hit > Riposte Interrupt/OA (crit > Free MBA)].
Lvl 12 Human Thief Daggermaster 22 Dex 18 Str
Feats- Cunning Stalker, Mark of Finding, Light Blade Exp, Nimble Blade, Backstabber, Silvery Glow, TW Fighting, TW Opening, Lasting Frost
Items- Bloodiron Dagger +3, Shard of Merciless Cold(Paragon), Frost Shortsword +2, Shard of Merciless Cold(Heroic), Gloves of Ice, Iron Armbands of Power(Heroic), Frozen Whetstones(Heroic)
Two Weapon Opening MBA
+23 Attack (6 Lvl, 6 Dex, 3 Prof, 2 Enh, 2 Feat, 2 CA, 1 NB, 1 WT) 90% Accuracy
d6+27 (6 Dex, 2 Enh, 3 Ft, 2 Itm, 3 WF, 2 LBE, 1 SMC, 2 GI, 1 TWF, 5 LF) 28-33 [30.5] | 35-45 [40] Crit
0.85*30.5 + 0.05*40 = 25.925 + 2 = 27.925
Riposte Strike
+24 Attack (6 Lvl, 6 Dex, 3 Prof, 3 Enh, 2 Feat, 2 CA, 1 NB, 1 WT) 95% Accuracy
d4+3d8+32 (6 Dex, 3 Enh, 3 Ft, 2 Itm, 3 WF, 2 LBE, 3 SMC, 2 GI, 2 FW, 1 TWF, 5 LF) 36-60 [48] | 66-120 [93] Crit
0.8*48 + 0.15*(93 + 27.925 + 1.8) = 38.4 + 18.409 = 56.809
Riposte Interrupt
+22 Attack (6 Lvl, 4 Str, 3 Prof, 3 Enh, 2 Feat, 2 CA, 1 NB, 1 WT) 85% Accuracy
d4+3d8+30 (4 Str, 3 Enh, 3 Ft, 2 Itm, 3 WF, 2 LBE, 3 SMC, 2 GI, 2 FW, 1 TWF, 5 LF) 34-58 [46] | 64-118 [91] Crit
0.7*46 + 0.15*(91 + 27.925) = 32.2 + 17.389 = 50.039*0.95 = 47.537
OA MBA
+24 Attack (6 Lvl, 6 Dex, 3 Prof, 3 Enh, 2 Feat, 2 CA, 1 NB, 1 WT) 95% Accuracy
d4+3d8+27 (6 Dex, 3 Enh, 3 Ft, 2 Itm, 3 WF, 2 LBE, 3 SMC, 2 GI, 2 FW, 1 TWF) 31-55 [43] | 61-115 [88] Crit
0.9*48 + 0.05*(93 + 27.925) = 43.2 + 6.046 = 49.246*0.95 = 46.784
DPR 103.593(OA) / 104.346(Riposte)
Edits: removed Pack Outcast, swapped out Vigilante Justice for Cunning Stalker. Normalized Lasting Frost on first attack.