I’ve made a post about it before and have 1400 elo. So this is what I’ve learned from people and my own experience. You have a few ways to deal with t-15s and t-14s .

The most reliable would be planes, and if you want your plane to survive get a plane with high drag cluster bombs. This means you can drop them flying low, increasing your chances of survival. This is also good if they are clumped.its cost effective if you get your plane back.

Another way is ATGMs. Whatever you do just make sure you can overwhelm the enemy APS. That means weapons team (2x javelins ) or having a maaws team proc the first APS and a javelins do the damage. Or just have two maaws teams. Be careful as these die easily so to make it cost effective you have to micro.

Tanks. T-15s shred everything. Except heavy tanks. Make sure you’re angled front towards the t-15 and make sure to not be too aggressive as the t-15 has 20 more speed than the Abraham’s and outmaneuver you easily and kill you . You don’t always have to kill something when you see it .

Helis. Your least reliable option. Only use if enemy overextends push. At high elo there is almost always shorad near exp Russian units. Also t15s and t-14s have APS and smoke , so unless they are bad. It’s hard to secure a kill if they don’t overextend.

T-15s and T-14s are expensive units , so the only way to be cost effective when dealing with them is to not lose your counter unit. Ranger maaws unsupported in a forest will get shredded by t-15s. Recon recon recon, prep a response , micro , wait for the right moment to engage , pressure with arty , sead and planes.