I don't know what content you are running at level 17, but I would guess you're doing elite vale, IQ's and the like. Mob hp starts to scale up fast starting from elite vale, and unless you are very geared you may have sp issues especially when you are soloing elite quests. A few reasonable options I would suggest to mitigate that are:
1. Group with people.
2. Solo your way to cap on hard.
3. Switch to a less sp draining savant. Air is arguably the most expensive savant sp wise. I recommend earth and/or water.
4. Make use of some dc based spells, i.e. insta kill spells. Since you have 42 dc I recommend prismatic spray.
5. Just get used to not being able to one shot mobs
You can't in ee quests anyways... Invest on efficient metamagic enhancements/clickies/items. Turn empower off sometimes.
edit: I recommend earth and/or water only for heroic levels. You'll have to make that decision again at lvl20+...