About the HB change: reduction of HP to 150 is excellent move to place it more in-between AI3 and FG.
There was very little reason to play against HBs, if you could hnadle them, then you could handle FGs too. So it is very good to separate the difficulties more.
In terms of thematic fit, I would suggest to also change the mark to 2x for them. I know that is a smaller impact, but it would be nice to have all perks change gradually from AI3 to FG, with the in-between step represented by the HB. We already have that in terms of upgraded cards, now HP so only the mark is missing to fit the theme.