Target-Practice, if you want a healbot, you can just take the healbot path in the catalog, and play with enhancements to taste. The only two things Radiant Servant did were to make the Empower Healing feat virtually essential on any build with 12 levels of cleric or more, and it also makes Charisma useful.

You can reset enhancements easily every three days, so don't worry about stuff like whether to have anything beyond Divine Vitality - try the others if you want, and keep the ones you like.

If you're already at level 17 on your warpriest, you also have the option of taking him to level 20, and doing a True Reincarnation into a 34 point build. That way, you can keep all of your existing bound-to-character gear, and you can go grind some more out (greensteel goggles, Gauntlets of Eternity, Torq, etc) before reincarnation that will make leveling up a lot easier.

Your Heal spell on a level 17 cleric is not affected by the warpriest path. The number of HP you can heal is affected by the number of cleric levels you have (up to 15), the Life Magic chain of enhancements (which you should fully maximize), by the highest devotion / potency item in use, and by empower healing. Your Heal spell should work as well as a dedicated healbot, apart from crits.

The best use of SP is based on the party, the quest, and the metamagics you have turned on. An empowered healing Heal costs 35 SP + 10 SP = 45 SP (slightly less with metamagic enhancements). A cure moderate wounds with empower healing and maximize both on costs 15 SP + 25 SP + 10 SP = 50 SP for far less healing. In a raid, mass healing is your priority, and cooldowns are your biggest issue, along with conserving SP, and knowing which metas to leave turned on (an area that I need more experience in). You can also spot heal with Heal scrolls.

For your build, maximize Wisdom, and have a healthy Constitution. Add Charisma and Strength to taste (10-12 is handy to avoid enfeeblement). A negative dex modifier is not a big deal - your reflex saves will be awful anyways, so don't even bother. Using a +2 Int tome at level 7 will give you an additional skill point at each level after level 7, so try to do that as well for a new character. Apart from additional skill points at each level, Int isn't all that useful for you.

The "Heal" skill is a waste of points - don't touch it at all, since all it affects is the number of hit points people receive when shrining with you nearby. Keep your Concentration capped when leveling up. I like to put my other points into Balance (helps you get up faster when tripped / cometfalled). Some people like Jump, but a ranger or arcane can give you 30 points of jump, so I tend to leave that one.

For weapons, you can use simple weapons (heavy mace, morningstar, quarterstaff, etc). Some of the best ones at low levels (and easiest to get) are the Nicked Heavy Mace from Sharn Syndicate, and the Pillar of Light quarterstaff from Catacombs (good for those skellies in Delera's). You can also get the enhancement that gives you Dol Dorn's Champion, which gives you longsword proficiency (nice lowbie ghost touch longsword in catacombs, Blade of Inquisition).