I suspect that if you don't have one of the newer BHs (esp Bossk) or don't have the older ones geared up enough then it'll be one of those "play the RNG" games for the entire week. The nice thing about legendaries is that they last for a week, so you have time to play around with mods, squad combos, and continue gearing/farming.
I would imagine 5* would be doable by anyone with the OG BHs geared up enough to do the IPD bounty. For 7* I'd expect you'd need to be able to beat the wampa bounty. However, you have an entire week to do it, and an entire forum full of people that'll post strategies, so for those that are almost there it'll come down to how much patience they have.
I have really bad memories of the thrawn event with g8 phoenix, but luckily I've got all the older BHs at 7*, g11 or higher, and some pretty awesome mods to play with this time.
