You must have been lucky then, cause, unless i use Doc, i take MASSIVE damage, thats why it feels like to me that if you don't use a healer companion, you just can't play the game, which makes me feel that bioware outright lied about the companions 'use any of them and not feel weakened by them' i surely do, from experience, its use a healer companion or be extremely weakened.
When i was leveling up the guardian, i was passing all the quests that people had trouble with, with no trouble at all with Kira and when it got to the point of getting Doc, the difficulty just got so high, it was use Doc or just die.
are you specced for tanking or DPS? using the proper stance for your spec? you're using all your defensive cds, right? interrupting when needed? killing the weakest mobs in a group first? got stims and/or adrenals? use medpacs? do all quests on a planet to guarantee that you'll be at the very least 2-3 levels higher than the next planet's minimum required level? it's not about being lucky. it's about making use of all your resources, and putting your gameplay knowledge into practice.
as far as gearing up goes, if you refuse to craft your own gear, then run flashpoints in your level range. they drop great gear. you can get to level 50 without paying a cent for new gear. the only time i use the GTN to buy gear is to get certain cosmetic looks.