Faction is a bit of a pain here. I've killed a couple hundred Seru guards (Legionaires and Hands) and my faction with most of Seru (although not the Heart and Eye, I think) has gone down from dubious to threatening, but Katta is still KOS, though I do get faction ups for Katta for the kills. If you can at all find a pinky druid friend, this is probably the best way to get this stuff. They should be naturally indiff to Katta, and they get a port to Twilight now, so it is a snap that way. All you have to do is collect the pieces. I've been buying mine, since the zones in which most of these pieces drop are BYOG and I tend to solo most of my time, besides which Luclin mobs are notoriously underconn. And at the level that you can do this quest, it's really not that great an armor. I'm currently 39, min level is suggested here as 45, but at 45 I should be starting one of the Velious armor quests. In any case, on my server, the Jewels sell for around 100pp, the marks from 50-100pp. The third components seem to be in the same range as the marks, and occasionally you can find them on vendors to whom people have sold to keep from having to spend the time in Bazaar. Off of vendors, the jewels are 19pp and some change, the marks are 7pp and some change, haven't seen any of the third or fourth components yet.
Good luck. Hope that helps.