I don't really see this as a net positive or a net negative as far as Andromeda goes. As far as Bioware bleeding talent, yes they are losing senior figures. Time for the less senior figures to rise. Bioware promoted the departed folks from within their own ranks and they achieved great things. I'm willing to withhold judgement, it is worrisome sure, but Andromeda likely already has the story set and edited, they've got a year to fix whatever went wrong(likely a game play issue, not a story issue, I'll confess, I'm assuming here, but it would be truly odd if the story was suddenly rewritten this late into development - look at Destiny for how that turns out.)
I'll get Andromeda day one, I don't think I'll be disappointed, but then Dragon Age 2 did happen, so it's within the realm of possibility, just not a realm I choose to believe exists because an editor and a lead writer left - if they're professionals, they would've left after their job was done. Which I wholeheartedly believe these individuals are.