Heal Tempest Staff GW2 Tempest WvW Builds
Tempest's mechanic is the overload. Stay in an attunement long enough and 
Singularity lets you channel that element into the area around you: healing and cleansing in water, might and burning in fire, a lightning nimbus in air, protection and an immobilising blast in earth. The same minor is what gives the spec its shouts.
Our heal Tempest is the aura build. 
Powerful Aura gives every aura you grant yourself to nearby allies, 
Elemental Bastion heals each ally you grant one to, and 
Unstable Conduit makes every overload produce another. It runs Minstrel's and a Staff, with Earth underneath for 
Rock Solid — the spec does have 
Stability, it just has to attune to earth to hand it out.
The four power builds are a 
Fresh Air package: crit, recharge air, burst again, and collect 
Transcendent Tempest's damage bonus for finishing an overload. Three of them — Spear, Staff and Scepter/Warhorn — share one Fire/Air/Tempest core and differ in weapon, two utility slots and a sigil. The Hammer one does not: it drops Fire for Water, which buys Powerful Aura, some passive healing for the people around you, and a 
Lightning Flash on the bar.
5 Tempest builds
Heal Tempest Staff DPS Tempest
4 buildsPlaying Tempest in WvW
Everything good about Tempest is on the far side of a channel. Singularity makes you wait in an attunement before an overload is even available, the overload is a long cast, and finishing it puts that attunement on a longer recharge. Get interrupted and you have paid the cost without collecting: no Transcendent Tempest damage, no Unstable Conduit aura, no 
Hardy Conduit protection for the people standing on you.
So the spec asks for position rather than reflexes. Healing, you want to be somewhere you can afford to stand still; on a power build, you want to arrive in air with Fresh Air up and a target that has already committed.
It is not defenceless. Rock Solid grants allies Stability on the earth swap, 
Armor of Earth gives you protection, Stability and barrier, and 
Diamond Skin cleanses off blast finishers. But none of the four power variants take any of that — the Hammer one at least carries Lightning Flash to leave with. That is a choice those builds make, not something the spec lacks.