I only have Level 4 Spalirisos, not Level 5, but its still better than any other physical dd weapon for Bst, except for level 5 weapon.
I also have fully upgraded Fernagu (Magian TP Bonus Axe) which I usually use in offhand w/ Spalirisos. I do have 2 different WS sets depending on whether I'm over attack capped or not.
Even w/ trusts, I can hit 80k on Locus Tomb worms (yeah, I know some of the lowest def Locus mobs). Its really fantastic.
I very much agree w/ Nalfey and Kaffy.
I can occasionally self skillchain w/ capped haste from trusts, and I have an almost perfect TP set. Which makes the tp bonus offhand a bit underwhelming in this way. can make up for it w/ pet often, cuz Blitz is so flexible w/ skillchain properties. but bst has all 4d level 2 properties... cycling them all pretty fun.
for tp building offhand I think the order is like this:
Kraken Club > Crepuscular Knife > Ternion dagger +1 > Agwu's Axe
However there is a special Falkirk slot in here... Digirbalag dark matter augment QA3 + DA3. I'm not sure if K club is more rare or not... but this ranks along with Crepuscular.. btw that DA3 in addition to the DA3 already on the axe... so iirc it was a total of QA3 + DA6. which is just a absurdly good augment of which I have never been jealous even though I don't think he used it for a long time. yeah, not jealous at all.
Hm.. I guess it might still be slightly behind crep. knife.. cuz dagger lower delay than axe.
I gave the Crepuscular knife to my dnc alt, so until I get another one, ternion dagger +1 is best offhand for self skill chaining... and its alot more obtainable imo. It has LOTS of accuracy to make up for the lower dagger skill. The subtle blow and wsd+ are very nice as well. Definitely worth making and augmenting if you are not quite up to farming Crepuscular gear, and still waiting for Lady luck from Up in Arms.
The only way i could make my dual wield tp set faster would be QA3 augments for Valorous gear.. (still need +1 from Gerdr belt too )but that's not a great option. the defensive stats are so poor that way... its only a toy for low level content where.. I really don't need prolonged skillchains.
(AM3 Mythic stp set is faster, but ofcourse, not using Blitz w/ Spalirisos in offhand)
slight nitpick @Nalfey. Bst gets 630 TP Bonus from Fencer due to job points Gifts. so 630+250 (from Moonshade) is 880.. meaning you only need 1120+ TP to get over 2k potency. not 1350.
as far as support jobs go best Damage will be BST/drk when in a well buffed party w/ Spalirisos. the attack bonus, last resort, and PDL + will make bigger difference on physical weaponskills.
If you are NOT overcapped with attack, /drg will do better weaponskill damage.
Warrior is not bad, its 12% DA, some attack and acc bonuses from aggresor/berserk but since tandem strike, we not lacking acc. and its still beneficial as a fencer build support job, but its kinda mediocre for bst. Like Nalfey said, the redundancy of fencer is annoying. Besrerk DOES stack w/ Rage. though you have to be pretty bold and suicidal to drop your def by what 75~85%? but what delicious attack bonus! (which you can get from last resort anyway) /war is not bad, its just not as good and redundantly redundant as a support job.
Dual wielding is easier to self skillchian, dnc and nin have alot of utility, but /dnc wins out in utility and flexibility. Definitely the most common support job for bst. NIn might be faster dd simply because you won't be distracted w/ as many job abilities to use, and just swing more... but it feels pretty limited. You get dual wield ofcourse, fantastic... thats the only dd buff from it. Utsusemi ofcourse fantastic defensive buff. and you get snk/inviz for utility.
However, /dnc *should have higher dd potential. (certainly for solo) If haste samba is up, you have a more efficient tp build (emicho gauntlets + Gerdr belt ftw), you have def down from box step. you have skillchain bonus 2 from support job which stacks nicely w/ Nyame for WS and you can cap skillchain bonus quite nicely this way. so dnc actually adds more damage+ options than /nin... but it wastes more time in ja's also. oh and self curing, faster movement speed, more efficient snk/inviz. the utility is fantastic.
/run or /pld are fine options if you are in the strange but delightful position of tanking on bst. (I really like this) /run being better for enmity ja's and magic def... but hey, shield mastery for tp is pretty nice w/ Adapa shield build, but a mix of Parry, Counter, and Shield block is surprisingly effective on bst for defense.
Also bst caps damage taken reduction more easily than almost any job. and we have lots of options for it.
I think I'm inadvertently saying Falkirk should update the support job section of the guide :D. ... oh wait, there isn't one. How rare. and its probably fine w/out it.
/mage jobs are for the legendary time when Pet parties were alive and well... /sigh
...but still nice for solo farming Mulcibar's scoria and other random old content.