It depends on the zone.

For Scars zones, depending on the Martello cores still in the Pulse Martello, your bonuses will vary. The more cores that the Pulse Martello has, the more your stats increase, including HP and MP.

Heroes zones vary based on the sphere of influence and overall morale. Since this is high, very often you'll see (under Morale Benefits or something like that) HP and MP Boost - Lv. 6 for example. This goes to show that you're getting a boost to HP and MP because of how well people are doing in Dominion.

In short, there are a lot of factors besides just abyssite, cruor buffs, and atma.