My current thieving level is 74. I understand that blackjacking is the best xp until 91, and pyramid plunder for 91-99. But i have become very frustrated from blackjacking 55-74 so far. Even though blackjacking may be faster, is pyramid plunder less frustrating?

Yes, it's far more enjoyable. Sometimes xp/h and gp/h aren't the only things which matter. I do it every now and then when I'm bored with blackjacking.

Blackjacking is horribly boring and requires constant clicking, I'd go with plunder.

Pyramid becomes slightly faster at 91, but it's really only a 20k difference per hour or so at 81. If you're getting frustrated at 74, I'd suggest switching then. The frustration is likely going to cause you to lose the difference in blackjacking anyway.

 

 

 

You can switch now if you wish, though I'd make sure you have all the quests that help with pp done. It just wouldn't be "optimal"