If there's a "trick", then I don't know it. I have helped fight Khal Ankur since the beginning of the event and I got all the halloween masks in the meantime. But it only happened once, that I had the boss for myself 'alone'. And back then I 'soloed' with two tamers - one a mage tamer with a chivalry "lesser" hiryu, the 2nd a disco bard tamer with a 5-slot fire beetle.
I use my sampire there to farm cults - sometimes I also fight the boss with it but I was never alone there. As told, my sampire "only" has an "ancient" suit - imbued only - three pieces are "artifacts" - Aegis of grace (+10 resisting spells), Jackal's collar, a studded bustier (major artifact), rest are valorite smithed and imbued pieces only. The "gal" is a macer, 120 macing, tactics, bushido, 110 anatomy or resisting spells, GM necro, 90 chivalry and 60 parry.
Since a good while, I'm running with bushido mastery (vol.3) active. HCI 40% (10% from conjurer's trinket), DCI 45% (20% from head piece), SSI 50% with town bonus & divine fury casted and a rangers cloak - LMC 45%. 113 hit points only (!), 183 stamina, 83 mana - 260 stats sum.
For Khaldun, I had only crafted three weapons yet, one black staff with SSI 30%, hit mana & stamina leech at 50% each, and hit fire area 50% and some damage increase - one tetsubo with 30% SSI, HML 43%, HSL 50%, hit lower defense also 50% and a war axe for armor ignore with SSI 30%, HML 56%, HSL 42%, HLD 50% besides some DI.
I always had / have to joust - knowing when to run or to stay and switch weapon is key and in Khaldun, I have to move all the time - also vs. the 'boss'. If the colored sparkles begin to intensivate, it's time to run back a bit before you get dismounted / disarmed / thrown back. If I missed that, I often found myself back in "grey scales".
Although I had to admit it - lately I had used the sampire "wannabee" from level one up to level four - then I'll get my tamer disco bard for the last phase of level four and the boss. Most times, I use my 2nd account there as a "rezzing station" for the warrior as I often collect grey robes - even with 120 RS, I'm sometimes just too slow or ran too much / too early or generally in the wrong moment.
During the spawn levels I switch between the black staff and the tetsubo - depending on the amount of mobs that surround me. For lesser crowds (2-3), I use frenzied whirlwind of the tetsubo - whirlwind of the black staff if the surounding crowd is large(r). For the boss I switch between the tetsubo and the war axe.