First and foremost, the point of view I'm posting from is one that has/had numerous clerics (one of which is a warforged), and numerous warforged characters of other classes.
The level range you are approaching is the roughest range (in my opinion) for clerics vs warforged. The levels where Stormcleave, Gwaylens, Greymoon & Co6 are done on elite, and runs through the vons and thernal start with "hey I can open this on hard/elite." I don't know of the numbers, but it seems (from a clerical standpoint) that at those mid-levels the number of hit points increase at a rate faster than a cleric's spellpoints.
For example, I have a level 8 cleric that stands with 660 (I think) spell points. This is holding a +80 spell point club AND she has a level of sorc, which puts her with more spell points than just a straight level 8 cleric. Keeping warforged upright at this point in the game for me can be a bit of a challenge when things start to go screwy. I'm still at the point where I can wand whip repair a Warforged with better benefit than using a cure spell on them, and primarily I do when able.
All of that being said, this is the best advice I can give you is this:
If you are going to stay straight fighter, always carry at least one level of healer's friend. Through the mid-levels if you're really worried about it, pick up the 2nd level. Once you start grouping with clerics that carry the heal spell (11 cleric levels), drop it back down to one level. If you don't pick up the 2nd level, instead invest those points into your WF con or DR to boost your survival. Get yourself to 100% fortification as soon as possible. At level 7 you can equip a clean mod fort item which makes you immune to crits. If you don't have one waiting for your character at level 7, find one with a quickness.
Keeping a warforged upright who has no (or minimal) healer's friend who is 100% fortified, has a bit of DR, and a slight con boost through enhancements is easier than keeping a warforged upright that neglects their fortification, has no DR, and doesn't keep the con up - but has full healer's friend. Just my opinion though...
Diplomacy: For when a fireball would just send the wrong message.
As an update: I just got my final AP for L16 on my Ftr13/Rgr3 (going Rgr now through to L20).
I redid my enhancements. I took all the DR ones, all the toughness ones, all the Str ones, etc. I had like 20 APs left over at the end, before taking Healer's Friend. I took all three and still had a few excess APs to spare on +1 Repair from Ftr and WF, and Item Defense, and other nice-to-have but not need-to-have enhancements. Maybe that speaks more to the lack of exciting Ftr enhancements than it does to the worth of HFI-III, but that's not what's up for discussion.
I'd say that if you have a fairly vanilla fighter, then you have the APs to spare for HFIII. If you have a class that takes up all your APs and you wish for more, then HFI is probably all you can afford.