I've been thinking about what could be done about boost without making it completely redundant, and my idea is thusly:
Make it not heal but actually drain health; make it provide damage resistance instead of healing. Say, over one activation of boost, you'd lose half a health bar, but all damage you take would be cut down to a third while under the effect (plus faster movement). Thus you'd have to use it at the right time (activate immediately before an encounter) to make it beneficial. If you boost "just in case" and it wears off without you entering a firefight, you've wasted/spent half a health bar for the benefit of moving faster across the map.
Damage resistance should only apply to health, not armor.
Speaking of which, assault armor should be halved as well IMO.