Need some advice regarding Nova and her powers.
Sure. I'll share what I've come to appreciate about Nova, the build that I currently use and the build that I wish I used.
I'm now at level 29 with her and thinking she might be the one, the one I use my first forma on.
Good plan. Most Warframes need at least 1-2 Forma to fully max out. Nova is one of the more useful frames in the game, so if you enjoy playing her then you should definitely Forma.
I basically use molecular prime only, maxed out streamline helps (what other mod do I need for efficiency and where do I get it?)
Used null star a couple times, same with antimatter drop, and only just equipped worm hole as a "what the hell, I have spare points, just as well stick it on there"
Molecular Prime is obviously Nova's primier ability, but don't write off Antimatter Drop. If charged correctly you can easily hit 30k+ damage from one explosion. It's one of the most useful nukes in the entire game because you can actually scale it up as much as you want when facing higher level enemies.
I initially thought that Worm Hole was kind of a waste but it's actually extremely useful. I suppose it's not "required," but it's very helpful for reaching the hidden areas and navigating the parkour rooms in the Void. You can also use it to position yourself in high areas where enemies cannot reach you, or even as a "get me the fuck out of here" ability when you get swarmed.
Null Star is pretty useless though. Forma a Defense polarity over its slot. Even in the event that you want to bring it along for some reason (what that reason is, I wouldn't know) it has a mod cost of 3 when maxed out. If it's placed in a matching slot it's brought down to 2. That 1 mod cost isn't gonna kill you. Especially since in all likelihood you'll never include Null Star in your spec.
The other Efficiency mod is Fleeting Expertise. It's a Corrupted mod so it comes from the Orokin Vaults hidden within the Derelicts. Look all of this up on the Wiki if you haven't done any Vault runs yet.
Now I'm thinking of changing her power polarity into either tactic or defence and probably again after.
Good plan. If I had it to do over again, that's exactly what I'd have done as well. I Forma'd my Nova before I realized that I wanted to use Worm Hole so I made the boneheaded mistake of overriding two ability slots rather than 1. Here's my current Nova spec:
I'm just barely getting by with Focus and Blind Rage in the "V" slots. That works out decently for low and mid-level enemies since together the mods fully counter the -60% Power Strength hit from Overextended. I'm losing a mere 24 points of damage off of each Molecular Prime blast while the radius is nearly doubled (90% increase). That radius increase includes both the casting radius for applying the Prime to enemies and also the
explosion radius when each individual Prime goes off.
In retrospect, I should have kept Worm Hole's ability slot intact and Forma'd over one of the "V" slots with a Defensive symbol for Overextended. In that situation I would keep Focus in the one remaining "V" slot, drop Blind Rage completely and replace it with Overextended (after the slot was Forma'd to Defensive polarity), and bring in Stretch to round everything out. That setup would allow me to use a Rank 3/4 Fleeting Expertise rather than a maxed one since I'd no longer have to compensate for Blind Rage. I'd still Forma another Defensive slot for Redirection/Vitality, but I'd leave one of the stock "V" slots intact for Focus.
If you crunch the numbers there you'll notice that my Molecular Prime blasts would only do 560 damage (rather than the normal 800) with that build. That's fine. Against high-level enemies Molecular Prime cannot one-shot-kill anyway. The real benefit of the ability is the speed and damage debuffs. Enemies taking +200% increased damage from all party members is
huge, and arguably a requirement for advancing to high wave numbers in Endless Defense or long durations in Survival
By prioritizing Range over Strength, the casting radius for Molecular Prime will be increased to
58.75m -- more than double the ability's stock range of 25m. The explosion radius when an enemy dies will also be increased from 15m to
35.25m. Do not underestimate how awesome that explosion radius increase is. You'll likely find your Primes doing overall
higher damage despite the lower base number for each explosion, since each individual explosion will hit just about every enemy in the room rather than only the ones close to it.
Yeah, fuck it. I'm gonna go ahead and Forma a third time and get rid of one of the "V" slots. If you plan it smartly from the get-go you'll be able to get away with just two Formas. Learn from my mistakes!
tl;dr - Forma two Defensive slots, one over a Warframe ability slot (top left corner) and one over a "V" slot (next one over). Leave one "V" for Focus.
Prioritize Range over Strength.