The power over life and death has been in the game the whole time. level 6 and beyond of the Colonies Capital ship. Once again Tel A ban of the Sin Universe.
Yes, it has always been there, and let's look at the Advent Loyalists for a moment, their theme is domination and control, mind control. Much like the Advent Rebels ability to bring the dead back, the Advent have always had the ability to mind control people, with the Rapture Battlecruiser, and a few more subtle things in their diplomacy tree.
What's important to note is that the two factions are taking these two themes of death/rebirth and dominaton/control, and dialing them up to 11. The Advent Rebels resurrect their destroyed ships and temporarilly revive enemy ships for their use, their people are willing to sacrifice themselves to harm the enemy or repair their Titan, knowing full well that death isn't the end for them. The Loyalists mind control entire planets, forcibly take control of mines and ships, forcing everyone to their cause, anyone who resists is killed.
Also keep in mind that the Advent aren't... really a religion, their use of terms like defilers and heathens has more to do with them seeing themselves as pure and enlightened, a greater form of life. They have no god that they worship, they do not kill in any one being's name, they kill for themselves and eachother, their collective mind, their Unity.
You talked about terrorism not being on military targets. I think of 911. As well as terrorist attacks on US soldiers. I have friends out there that are US military people. So don't tell me terrorism can not be against military. As well killing of an entire planets population as your bomb. That is Terrorism.
I said tended, and explained exactly why.
How is it terrorism, exactly? Because people are sacrificing their lives to do it? Terrorism is about goals, not methods, the goal of Wail of the Sacrificed is clearly to cripple enemy military assets and give the Advent Fleets an advantage in battle, not to terrify or intimidate the enemy into submission, which is what terrorism is about by very definition.
Edit - Oh yeah, with regards to the Rebels in general, this is from the Diplomacy lore:
"Some members of the Advent started to wonder if their course of vengeance was the right one to follow"
Those are the ones who pushed for diplomatic relations, and by the sounds of it are the ones who splintered into the Advent Rebels.
Well, we don't know for sure, as this tech doesn't work. But the tooltip says destroyed ships will respawn at your homeworld, and their are two research levels that increase this by 5% each, so maxed out it sounds like whenever one of their ships are destroyed there is a 10% chance it gets revived at the home world.
I never noticed the homeworld part, it strikes me as a bad idea, homeworlds are often far from the frontlines, which means cost or no cost, it would often be better for you to just rebuild the ships at frontline factories, instead of having ships respawn at your homeworld taking up your fleet supply and being 8 jumps from the front.
It would be more worthwhile in my eyes if they just revived on the battlefield.