Let’s go over some of the basics.
Fireteam has access to, in no particular order
A Sniper Rifle which kills in 5 body shots regardless of the Class with the only Class naturally able to survive more than 5 being Mr Black who was JUST added and is likely to get nerfed in one way or another in a couple of months.
A wallhack ability which reveals the Predator’s exact location for as long as 9 seconds in which time you can see them through walls & cloak regardless of distance AND depending on Specialization either applies a 10% speed debuff to them or makes them take 15% more damage.
The ability to solo kill Predators in 2-3 seconds with a PISTOL at point blank range in a game where up to 4 people can be firing on them at the same time, WITHOUT damage buffs. Speaking of.
Certain classes such as Assault; Scout, Dutch, etc can Damage Stack and buff their Damage output by anything from 20% to 50% based on their Perks & Specs & possibly team comp. Keep in mind, the game is currently balanced in a way that only 1 out of 4 FT players is needed to kill a Pred in seconds, so guess how that ends up.
Oh and then there’s Field Medic which makes getting Kills even harder because they can rush over to a downed player and revive them in a flat 1 second, 0.8 with Dexterous equipped.
And adding on to that they added Bots to FT which have 100% Auto-Aim in a game with Hitscan weapons in a range of 60 metres whilst uncloaked & 10 metres whilst cloaked and each Bot can be hijaked by a Dead player to revive themselves if they do get killed, thus skipping the entire Reinforcement mechanic.

