I tested Rush of Agony, a while ago, and noted that you can have both Ulfsild's Contingency and Teleport Strike on the Rush of Agony back bar. You bar swap during the teleport to your Vicious Death front bar and all the damage only goes off at the target location. You can obviously pile Proxy Det on top of that. This leaves room for Balorgh plus a mythic and 1x Trainee.
Turned out that I don't have the patience to make bombing builds work myself, e.g. to wait for the right opportunities. I briefly tried the above with Contingency, but without Proxy Det, so as to have a shorter windup time. I found that very underwhelming, but I suppose I didn't give it a chance. You may want Rally on the back bar to gain Major Sorcery / Brutality in advance and while cloaked. In that case you might go for Siphoning Attacks + Shadowy Disguise on that bar as well. The combination of those 3 skills supports prolonged movement in cloak.
Malcolm used Dark Convergence in the last bomber video I watched of him. It seemed like he put some work into it and tried a few things. It is possible that Dark Convergence plays better than Rush of Agony, even if the latter has the reputation for being particularly broken. That said, I'd stick with Rush of Agony for a while.
You may want to fit Race Against Time for escape + the crit buff, Ulfsild's Contingency, Telport Strike, Proxy Det, an AOE spammable, Relentless Focus for extra passive damage, Shadowy Disguise, Rally, Siphoning Attacks. That's 9 skills already. The last skill might be a self heal, Concealed Weapon for attack and the passive speed, or perhaps Shadow Image. Shadow Image has verticality, allowing you to port back to the safety of a bridge or building in IC, or to a keep wall or tower in Cyro.
As regards the AOE spammable, I was trying to make Brawler work, e.g. with the Master's 2H from Dragonstar Arena instead of using a mythic and 1x Trainee. This scales your AOE damage with the number of enemies. With a high number of targets, it can deal more damage than Whirlwind and will do so regardless of their health.