As for the dark cloak vs shadowy disguise discussion, I chose dark cloak. For offensive PvP, it's a must in my opinion. The way people pour oil in keeps, I'd never run into one without it.
If a player spends all of his or her time at sieges, I could see how it may be useful.
Sieges don't interest me though.
"If you want others to be happy, practice compassion. If you want to be happy, practice compassion." -- the 14th Dalai Lama Wisdom is doing Now that which benefits you later.