Advice on my gimped 7h build

HYou seem good for direct heals and prot but could perhaps use more party heal, maybe on the paragon. Yeah, the Paragon could bring party heals but it'd come at the cost of losing your Command skills, else you'd be spreading your attributes too thinly.

As "Stand Your Ground" is your only global party damage reduction (and you definetly need one of these in most fast reasonably effective team builds that you don't want to have to stop and think about before every pull in HM), then you'd have to either fit it on another character, or indeed replace it with that "They're on Fire" idea you were thinking about.

You could quite easily adapt that into your build though, with some simple changes.

For basic starters, give the Elementalist Searing Flames, for one source of constant mass burning, and adapt one or two of the other skills to compensate (probably dropping Rodgort's for some more energy-management to make up for the loss of Elemental Attunement).

On the Ranger swap Volley for Barrage, drop Rampage as One for Call of Haste (the pet can use the speed buff and attack speed increase, but if the Ranger is just spamming Barrage probably won't need it themselves, Call of Haste is also a Shout, which will be important in a moment), and swap Sloth Hunter's Shot or one of your Ranger 'rupts for your team's third Rez (as the Paragon will be losing his).

Then, taking a que from Khomet, give the Paragon a Ranger secondary and let him wield a Bow with something like the following:
Marksmanship 10, Leadership 11+1+2, Motivation 10+2.
Barrage, Distracting Shot/Anthem of Flame, They're on Fire, Burning Refrain, Glowing Signet, Chorus of Restoration, Aria of Restoration, Ballad of Restoration.

You could also consider giving the Dervish one of their own skills that cause Burning to adjacent, if you felt you wanted a third source of Burning.

Have the Paragon use Burning Refrain on himself and the Ranger as secondary sources of mass burning, whom both can then spam burning on multiple opponent's in HM by spamming Barrage (which will also work well with your Ritualist's Splinter Weapon), as enemies will nearly always have more health than you there since the HM changes in the Elementalist update last month (unless they are near death in which case you don't need the damage reduction from burning anyway as they are no longer a threat), to meet the requirement for They're on Fire!.

Anthem of Flame would maintain it in between fights, though if you don't mind recasting it (or going to the trouble of manually having the hero alternate between spamming his healing Anthems out of battle to maintain it), use Distracting Shot for another nice 'rupt.

Chorus of Restoration and Glowing Signet would keep the Paragon's Energy high, despite the Barrage Spam. The high Leadership score would basically make the Chants almost pay for themselves. Chorus of Restoration would be a party heal that the physical-only classes (the Ranger and the Paragon) could trigger, Aria of Restoration a party heal for the rest (the casters), Ballad of Restoration as a weaker party heal for everyone. Alternatively you could drop either Ballad or Aria for Song of Restoration, then take Volley instead of Barrage, though I'm not sure it'd be worth the reduced damage output and burning spread.

This would also introduce a few synergistic elements into your team, which as you noted, for the most part you lack.

It wouldn't be an optimal set-up, and you'd probably be better off switching some professions out for others (like using a Monk or Ritualist as your party healer instead of a Paragon, or a Soul Twisting Ritualist for your global party damage reduction), though those are my ideas of what you could do with keeping the current 'theme' and hero set-up of your current team consistant and intact.

I will have to be the odd-one in all this; I find playing a backline monk very fun. With pure heroes, not as much as with a real group of people though, but fun none-the-less. I just wanted to agree with this. Healing/protting is pretty fun in my opinion, and I actually like it more with heroes than with people because it there is less pressure on you if you accidentally mess up and let someone die.

@ the OP: I'v tried Khomet's odd bow-wielding paragon setup and was not really impressed. I would just stick with a spear on the para, and focus on command support + single target dps.