"decrease the damage by 15%-25% and especially the radius by 30%-40%"

So basically just make it the same as missile rack :-). That would leave no difference between the two weapons.

I don't know what SP and level you're playing at but such weapons typically only feel overpowered at the early stages of the game. I'm at 5k-6k SP and I both use and face both weapons. The issue is often not so much the weapons but the fact that some low power players face high-powered players with such weapons because of matchmaking.

After some time things balance out, and you of course also have the option of picking them up. Variants of both weapons are available for credits. 

Geminis also seem OP in the beginning, but they are slow and usually easily avoided. Just stay away from the edges of your hiding places.. there might be some bug that lets geminis hit you even when it seems unlikely that they can.

Neither of them need a nerf.

Stormracks and geminis definitely don't need nerfing, I'm maxed everything, I use stormracks 16s on my deathwalker, all maxed with maxed implants and I use maxed gemini 16s on my outlaw with all maxed legendary implants, and stormracks on deathwaker in high power matches take about 2 or 3 rounds to kill a mech same with maxed 16 geminis, they take about 3 or 4 rounds to kill mech, but all my opponents are all maxed with maxed mods 

So no they definitely don't need nerfing, if anything they could do with a damage buff, 

And like tar said, they only feel powerful in lower hanger matches, so if I was you I would just get those weapons yourself so you can compete better against players using them, nothing should ever be nerfed, everything is balanced and a few things actually need buffing 

you are although silent about which weapons dont need 3-4 rounds to kill a maxed out mech, which ones are they?

The only 2 mech and weapons i've found that kill a maxed mech and maxed mods in one round are. 

Seeker with burrow beams, but you need the legendary burrow beam damage and mag size implants, and also legendary seeker bonus damage implant, I kill every mech in one round with that, and also 

Orion and gemini 12s,and you need the sheild piercing legendary implant and legendary gemini damage implant, and that normally kills most mech in one round, some might take two rounds though but only just two rounds, cos the first almost kills them, one round is usually enough cos bots fire at the mech while ur geminis shots are heading towards it

so gemini is op after all ? ;) joking.. sort of.. am i. 

The meta is shifting more towards the Guided weapons category, and that isn't good to me because I don't have good Guided weapon counters (except Eclipse)

Only really on orion because of the 150% extra damage you get on geminis from orion hunter mark

To be honest I feel like one of the only players in the entire game to not have any of these overpowered mechs and weapons. And you are also right about the matching up with much higher players because I play battles that have those maxed weapon loadouts that you mentioned.

In the past 5 or so battles ive played today (I'm an inventory power 20k) I've faced against players with 40k-60k power, making it an extremely unfair game.

Inventory power is not a very good measure to know the strength of an opponent (infact I find several meta-driven hangars at 10-15k inventory power). I have about 17k inventory power, but I have pulled up a couple of useful mechs and weapons from recent ECRs. I'd recommend you to save up enough credits and A-coins to guarantee the mech/weapon you want from the ECR.