Depends what you wnt Ember to be? If your looking for a tank, Overheat, Focus, & Continuity mods will have her reducing 91% of all incoming dmg for a good while when Overheat is used. Crowd - Control? Fire Blast, or World On Fire along with Focus & Continuity will have her burning all thts around her but if you perfer WOF as your main move for killin, you can also toss in a Rush move so she can run faster while using WOF maybe a Marathon mod if you like to run miles on end while WOF is in use. Hoped tht helped ya
I have say that I built my Ember after she was supposedly bugged or nerfed and I still love her. I love being a walking furnace of death, so I use continuity, flow, focus, constitution (I tihnk that is the name of the new mod that extends duration), stretch, and occasianlly throw in a marathon/rush or redirection/vitality depending on the situation. She is a bit squishy without her damage reduction power running, but she is a walking deathtrap, especially for infested. Also one of the fastest frames for me to run and farm with just because anything that comes near burns to death while i am free to loot chests/lockers.
This is my embers current layout. Since world on fire really is the bread and butter everything is geared towards the most damaging and longest possible. I still need to forma it one more time to cap all the mods, but you get the idea. I personnally dont run fireblast because I feel the damage reduction from overheat outweighs its useful, since it allows me to basically ignore a toxic ancients poison(makes it tick for 1-2 dmg).
I got Stretch, Streamline, Flow, Continuity, Focus, Max redirection, Fast deflection, then WoF Overheat and Fireblast. No vitality mod since ember has really low life I dont find it worth of the energy points engaged in it. Prefer high shield regeneration rate with fast deflection you only have to worry bout toxic units