Since the vocation adjustments, I don't think the best strategy is to keep throwing runes all the time.
For me, runes are more of a filler now, and I mainly use them whenever my elemental spells (ice and earth) aren't effective because the creatures are immune or highly resistant to those elements.
On the other hand, if I'm hunting in a spawn where creatures are weak (or at least not resistant) to my elements, then most of my damage comes from keeping my offensive spells on rotation and casting them as soon as they're off cooldown.
As an ED, this is what I personally prioritize:
1) I almost always use the forked spells (my team actually calls them "the druid's crazy chains" ) while we're approaching a box or moving from one box to another. Basically, whenever the pull is still being built or the box is already breaking apart and another wave isn't worth casting anymore. The chain has great range and is really good at hitting monsters that are still scattered around.
2) I use my waves whenever my positioning lets me hit most of the box. Personally, I use all of them: exevo ulus frigo/tera, exevo tera hur, and exevo gran frigo hur. Once I see that most creatures are already in red-black HP, I usually finish with exevo gran mas frigo/tera, since by then I can normally hit the whole box.
3) I use SD (Sudden Death Rune) if there's only one creature left while we're already moving to the next pull. That way I can keep contributing damage without slowing the team's experience down.
In a team hunt, as the ED, my priority is still keeping everyone alive. I'll use Terra Walls or other field runes whenever they're needed to protect myself or the rest of the team.
Because of that, I almost always use Shared Conservation whenever we're hunting a new spawn, if there's any risk, or if we aren't hunting with our usual four-player team.
Once we're comfortable and confident in the spawn, Elemental Synthesis becomes my go-to stance. That extra 10% Magic Level makes a noticeable difference to the damage from all my elemental spells.
This is simply what has worked for me. I usually hunt in a standard four-player team (EK, ED, MS and RP), and I'm currently level 787.
Of course, there are many other ways to improve your overall damage. Charms, preys, equipment, magic level potions, etc... they might seem like small upgrades on their own, but together they make a noticeable difference over the course of a team hunt.