Moldy Buckler drop rate is rare. I think was about 1/20ish. Pallas is definitely harder than Alkyoneus. I got triggers and soloed both as 75NIN/THF and lucky for me there was a SMN nearby curing me. Pallas is harder because his pet bat eats utsusemi and takes about 3 WS's to kill. Just ask the other real campers to help kill the bat and they gladly will help any non-RMT.
Alkynous is easy but if he spams his lightning breath move, he can be hard. I recommend taking potions unless you have a healer.
The RMT don't dominate the area like people say at least on Siren. There were plenty of gigas and the ??? was up for several minutes.