If your on the front line and don't have some crazy good R/EX pants already, then you need to have these. Any job that can use these as a DD will use them till around lv. 70 from what i've seen, and the 70k price tag on Shiva isn't bad at all for what it gives.
Unless you've already acquired godly EX leg armor, I'd keep rockin' these as SAM until you do. Even after 70. Make sure to macro your Myochin Haidate after you get Tachi: Yukikaze and Tachi: Gekko, though!
these are okay to maccro in on samurai but when you get a chance on getting shura legs i suggest you sell these imediately and dont touch them again on samurai