Hmmm, Well, I thought i saw math with Paraz+1 being garbage due to a 50/30/20 proc rate on 1/2/3 hit. But it was a long time ago and I think it was even before +1 was available so, IDK :|
Anyway, Your options are simple, Kila+1 are the good Damage ones, easiest to get in terms of "High Damage" daggers.
Basically, DEX Kila is your best bet, Inside abyssea where you'll spend most of your waking FFXI life, if you have any respectable Atma's (and i hope you do with apparently owning an Amano?) you'll likely be @ or near fSTR cap for daggers, making the STR kila fall slightly short.
that and DEX being a primary mod in well, every THF WS outside of Mercy Stroke.
now, Fire Kila is also an option, if you feel you'd get more use out of it, I'd suggest at least 1 of each.
The Trials aren't too hard, Weather gives you 5 points per kill, so it really speeds things up, that being said Fire weather is a lie, shits rare to find even in the heat seasons, but it wasn't too bad for my h2h, should be easy.
DEX (Thunder) Trial is pretty simple too, except for the Qutrub part... *** Qutrubs, yes. Your best bet is to shout for a large group (Blues too, for Spinal Cleave/Hysteric barrage, you will get aggro from lamia) and go on Thundersday, if you have free-time spend it in Caedarva hunting thunder weather and taking out the qutrub there. @ level 85 its much easier.
Parazonium+1 (O.a.2-3x path) is simple in the way it requires nothing more than the mob family yields exp. no Day/Weather reqs, but the first 3 trials are NM camping Trials, which aren't bad but are annoying. That being said, if you wanna have a hellish repeat of Amano trials by killing anywhere from 200~500 of a specific mob family roughly ~6-7 times then this trial will be simple for you.
Auric Dagger if i recall is becoming/is obsoleted if you have any sort of major haste buffs on you, march, haste, Samba, etc, what with Dual wield apparently effecting absolute haste cap (/sigh).
Rapidus Sax would make a good offhand, with that being said, if you didn't want to work on Parazonium+1.
Either way you want your main hand to be a strong one, The Empyreon/-1Emp are both more powerful than the Kila+1's, but take significantly more time.
The empyreon itself is absolute piss cause you need Glavoid shells, not a hard task now adays (wasn't even too hard then) but its annoying, should be able to burn through it if you dedicate, but my guess is if you were a Blau/THF knife full time THF you probably don't care too much about the job, at least not enough to invest in an Empyreon.
Either way, Kila+1/Rapidus/Paraz+1 is your best bet. Rapidus drops from Amhuluk, Amph NM in Abys-Misa.
Also, for Empyrean/Kila set up the guy above me listed, DEX kila would smash the ***out of STR kila, the Empyreon WS has a strong DEX mod, and no STR mods, and as i mentioned above with Atmas...