Someone told me today to stop using DPS spells like Stone

[Deceptus]

Just look at trusts and squadrons. SE programs the healers to DPS if your HP is above 50% (or the tank) and to start healing, if your HP is below 50% (or the tanks).
Pretty similar to what its like in normal 3 mob, single group, trash pulls.
This is also why they suck at healing double group pulls, since you need to start healing at 60-70%+HP depending on factors. (plus the AI is roughly 1 second slow to decide what action it will take next. It really should be adjusted to 60% at the bare minimum.)

Hell, often times in trust I'm UNDER 50% hp and dropping and still don't get healed.

Looking at you Alphinaud you pathetic excuse for a healer.