I've been putting some thought into this recently. I'm inclined to think that the following is the best, outside Abyssea.

Code:
Main	Kannagi
Sub	Kamome
Head	Maat's Cap
Body	Iga Ningi +2
Hands	Iga Tekko +2
Legs	Usukane Hizayoroi
Feet	Lithe Boots
Neck	Hope Torque
Waist	Warwolf Belt
Back	Atheling Mantle
Ear1	Centaurus Earring
Ear2	Brutal Earring
Ring1	Epona's Ring
Ring2	Rajas Ring
There are a few reasons why I choose this build. To begin with, mobs outside of Abyssea, the higher level ones you'd be fighting at least, are going to have a defense of between 350~400. This means you'll need 700~800 attack to cap your cRatio. It takes +52 STR over the mobs VIT to cap fSTR and +50 DEX over the mobs AGI to cap dDEX. Here's some more data regarding attributes/stats with the different gear.

Code:
Slot	STR	DEX	AGI	DA	TA	Attack	Accuracy
Base	87	81	81	10	0	388	353
Main	0	0	15	0	0	0	0
Sub	0	0	0	0	0	8	8
Ammo	0	0	0	0	0	0	0
Back	0	0	0	3	0	20	0
Ear1	0	0	0	0	0	10	0
Ear2	0	0	0	5	0	0	0
Neck	0	0	5	0	0	7	6.3
Head	7	7	7	0	0	0	0
Body	12	12	0	0	0	17	17
Hands	0	10	10	0	0	0	8
Legs	5	5	0	0	0	10	0
Feet	0	6	6	0	0	0	0
Waist	5	5	0	0	0	0	0
Ring1	0	0	0	3	3	0	0
Ring2	5	5	0	0	0	0	0
Food	7	0	0	0	0	23%	0
Total	128	121	124	21	3	524	452
This is for a 90 Hume NIN/WAR with 5 STR merits and 8 Katana merits. The total attack did not take food or Berserk effects into consideration. With food up, you're at 644 attack. With food and Berserk up, you're at 805 Attack. So you're just barely hitting the cRatio max in a lot of cases (with Berserk up) rendering more Attack useless. Accuracy is also going to be capped, it caps much more easily than Attack. Mobs would need at least 77 VIT to uncap fSTR and 71 DEX to uncap dDEX, which is just above what Limbus and Dynamis mobs have (I think, might be wrong.)

I've a little bit divided over the waist, to be honest. Anguinus Belt is a great piece, 15 Attack and 1 DA is quite a bit, although I'm not sure if it's worth it because dDEX is close to uncapping and losing those first few points of dDEX results in a considerable critical hit rate loss.

Alternatively, a more attack heavy build might be nice to have while Berserk isn't up (or when you don't even have access to it, i.e. DNC subjob.) I have yet to brood over what that might be though, or even do the math to see if it could be worthwhile. It's more of a gut feeling.

Also, Epona's Ring might be replaced by Stormsoul Ring. Before the ring, you'll have a base Double Attack rating of 18%. Because this can proc on both main and sub, it equates to an average of +0.36 fTP (assuming 100% accuracy, which will be done for everything else in this comparison.) Blade: Hi is going to have a base fTP of 4.0 + 1.0, thus your average fTP is 4.0+1.0+0.36=5.36. Epona's is going to bring your Double Attack rate up to 21% and introduce a 3% Triple Attack rate. Assuming that Triple Attack procs overwrite Double Attack procs (going to be a small difference either way) yields an increase of 0.53 fTP for a total of 5.53, or a 3.13% marginal gain. WD, under capped fSTR conditions and 124 AGI is equal to 144. Stormsoul Ring will bump this up to 148, which is only 2.78% marginal gain. Your WD, pre ring, would need to be around 128 before these two gains were equal (which I don't think is going to occur outside of Abyssea.) However, if your pre ring AGI total ends in a 3 or an 8, then Breezesoul will add 5 to your WD, which is at least a 3.47% marginal gain.

I don't think Loki's Kaftan is a good choice outside of Abyssea. Although the critical attack bonus yields a higher marginal outside of Abyssea (due to no Razed Ruins), a much lower base critical hit rate is going to bring the overall marginal gain down by quite a bit. It's impossible to say without knowledge of how Blade: Hi critical hit rate is affected by 100%/200%/300% TP, but the 6/7 WD increase and occasional critical attack bonus is probably surpassed by 17(23) attack, maybe 3 fSTR, and 5%+ (to dDEX) that Iga Ningi +2 provides.