Wait, I don't understand at all. First off, what is the new hp system? Full Con score + HD (is it still rolled -- if so, don't worry the high HD classes will get shafted plenty as the rolls are too infrequent for the law of averages to take hold) +bonus? What is "bonus"? Does this system typically result in much more bloated hit points, or just as early levels?
It results in an additional CON score worth of HP which you get at level 1. The point is to make players not get 1 shotted in the low levels.
As for healing, if your group was already using wands of lesser vigor for out of combat healing, it may not be a big issue. For 750 gp, you get 11 hp/charge x 50 charges, or 550 hp healed for the cost. So keeping the high hit point meatshields healed isn't necessarily that hard.
Hmm. I was not familiar with this magic item. They've been using potions. buttloads of them. current group has 3 players and no cleric, so although the druid can do SOME healing, the players have to stock up on healing potions. I give them to them at half cost though. but the issue was that they were healing too slow so I upped the hp they give by d6. I'll have to introduce those items into the game though.
I'd be more worried about the poor direct damage focused mage, who is already the weakest of his lot. I mean, come on. A fireball's been d6/level, max 10 since at least 2E, when people stopped gaining actual HD to hp after like level 10! Just a flat 2 or so. 3E made high level hps much higher, and if this system works like it sounds, it's further doing this. I suspect this is what you meant when you mentioned giving more spell slots?
That's exactly what I was referring to

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That wouldn't be the answer. The save-or-die/lose/paralyze/cry/join the dark side spells don't care what hp the guy has, so giving more spells per day only helps them more. You'd need to go and just give evocation spells larger damage outputs. Perhaps instead of manually doing this for every spell, it'd be easier to make blatantly good feats to help with this like...
We play with no direct save or die effects, but the other save or X spells are there are there. Save or die spells aren't directly removes, but they instead do ability damage or normal damage depending on the spell.Phantasmal killer for example. instead of die or 3d6, it's 6d6 or 3d6. Maybe we should change that 6 to a 9 to compensate for the extra HPs though.
I don't want to make them take a feat to not suck. So maybe I just go through the spells and up the die types. Make fireball do d8s or d10s.
is that the suggestion youre proposing?
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Just in case you were wondering, this is used in conjunction with other rules changes. it's 34 point point buy, for instance. But npcs get the same amount of extra points(9). The reason for the extra points, is Stats become much more important with the variant rules we're using. CON and class switch roles for HD type, Skill points are based on INT+WIS with a smaller bonus by class, Dex is always used to hit, Str for Damage, (unless you take the inverse of the old weapon finesse feat to use STR with particular weapons), CHA is used for WILL instead of WISDOM. The result is that everyone needs every stat to varying degrees. It's a bit of an aside, but I thought I'd mention it. So far it's working out well. Class is less important now. It needs tweaking, but I think it holds promise. The players like it too. It means the caster can have better HD if they want. Course, one player was minmaxing during his first character creation and realized that doing so would give his barbarian a d4 HD. that was funny. Oh. I should note, that the main goal of all this, was to make minmaxing more difficult, as well as have every stat be useful to everyone.
The only problem I'm having with it, is because of a shorter skill list, everyone has too many skills. I think I might switch skills to something like in pathfinder where you dont put ranks in skills and skills are done more like in 4e. I'd probably go somewhere in between though and have a few levels of competence.
The more I play D&D the farther we get from core rules. eventually I'll just print out my own phb

and eventually wont be that long. I'm already like halfway there.
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Back on topic:
So how would you suggest I alter damage? just up all evocation spells by 1 damage type? maybe just add a d4 to all of them? what would you recommend?