It's quite a broad question as many here will have their own preference and idea of what is good to them.
Here are my two cents:
If you want to take advantage of the Sub and Dual skills shared by the character then you would benefit from a support class (defensive). A tank, another iss enchanter, healer, even tyrr dreadnought.
The same is true of gear. However, Heirophant is best suited to light armour due to the cd reduction and other perks of the light set bonus (at +8). I would be tempted to play a hybrid issue/iss in your case. Either heiro/doomcryer for the crier harmony or heiro/bladedancer for the lvl 2 warrior harmony. All 3 of these are popular with pts and dds and will help you to get into pts and benefit them the greatest.
With the continuing 'free to play' theme creating an unbridgeable gap between those who spend and those who don't. You'll want to maximise the crossovers between your main and dual.
If money is no issue, then damage dealers are great fun to play. However if you want to progress in the game and be useful in a pt set up, go the support route. Supporting others will teach you the core game mechanics and enable you to become a better player.
Consider whether you will play another character to pt this one. If so, you can have a complimentary mix.
Hope that helps you to decide.