Nyzul is the best thing to team up for; 3 players is the sweet spot, but 2-4 is fine. A party of 5-6 players for Nyzul is more hassle and won't boost the amount of tokens by much, if any at all.
As for Einherjar, if you want to make it easy, level bst and put some random gear together. Use the cricket, and switch to fly if you get the Cerberus boss. Spam T3 for a week or two.