I can't comment on the classes you mentioned, but I am playing a Sage, specced deep into the healing tree. I am leveling that way, and based on what companion I use and what I am fighting, yes, the abilities I use change a lot.
And it's FUN to have a choice sometimes. When I fight quest-bosses (basically, tough elites with different abilities) and use my tank-companion, I have to find out quickly whether I have to focus on healing only, have to react to damage spikes etc.
Then, some bosses or mobs require me to cut back on the healing and contribute DPS instead, sometimes from a range (to avoid AOE dmg), sometimes up close, mixing spells and saber-strikes.
Is it complicated? No, but it requires me to react quickly, and adjust to different situations, and that, to me, is fun. It was unusual at first, because neither did I find myself using the same rotation over and over, nor did I find myself only healing or only DPSing.
And I like it, especially when it gets to using different companions for different situations.
There are not many guides, and I know a lot of people seem to be confused, but at least in the case of the Sage, which is my main, I can say that, if you experiment a bit and set up your action bars in a certain way, you can figure out some combinations that work for damage, some for healing (and emergency situtations), but still you will find yourself changing tactics a lot. I dont doubt that other Sages might use a different combination, or maybe some actually use a strict rotation, but so far, I have survived many tough fights, some against really tough odds (Champion level 4-men boss solo, being only one level above him), and so far, it's been challenging as well as a load of fun.

On your operative, with your DPS spells...did the mobs go down? Did you find yourself struggling a lot? What about your friend? Because, if both of your methods work, if the mobs and "quest bosses" go down, then neither of you is doing it wrong IMO. Yes, if he kills a tough mob in half a minute and you take, say, 5 minutes, maybe yours isnt efficient, but I doubt thats the case, so I guess both of you do it right.