The Bond isn't an issue, if you are leaving to double, or triple, your salary.
I spoke around a year ago to one very experienced guy, who told me that many of them told NAS (in a nice way) not to plan on them being there long term with the current T's & C's.
As he told them, various European bases are being offered by Chinese carriers on Commuting Rosters, +, as the aircraft is growing in numbers, many more opportunities are coming up, which he & his colleagues were obliged to consider.
NAS's reply was reported to be "Yeah Yeah we know, stick with it, it will get better"
Last I heard they were struggling to get new guys trained (won't have been helped by Virgin Atlantic guys going back to fly their own) but, if it is as you say, and the exodus has already started, seems the message didn't get through quickly enough. The operation has had enough problems, without adding crew shortages to the mix.
The conditions are wholly underwhelming for a Wide Body contract job.
Don't think the CC from Stateside are in a very happy place either. What they foresaw as a few days (out & back, or maybe with a quick BKK thrown in ) has (I am led to believe ) metamorphosed into 21-23 day rotations on occasions (as I discovered when I asked why their Crew Suitcase was quite so big )