We had a group going for awhile but it kind of dissolved. There are frequently shouts in whitegate for pick-up grops, even at the lower mercenary ranks, you can probably check that out.
The major difficulty with the assaults is the limitation based on mercenary rank, and seeing as you can only do up to 7 assaults a week, it makes it hard to rank up quickly.
Every now and then we will do a quick pick-up party in the the linkshell (I think we did one late last monday) just to get some quick assault points when people are bored.
Consider mentioning it in the LS sometime when a lot of people are on (like in the early evenings) and see if you get any people to bite.