Let's take a little time to explain this tierlist. Note that this ranking applies to team play (understand by that premades of 3 to 5 players). You can find our ranking for solo queue in our dedicated tierlist!
Sage: If there's really ONE must-have character in premade, it's Sage. Her abilities are a real gam, with care for herself or her allies (and several times per round!), the Slow Orb is ideal for delaying a rush or to combine with the abilities of other allies (the skillshots and other offensive skills with hit their target more easilly), the Barrier Orb which can lock an entrance or boost your allies, and finally this incredible ultimate which allows to play 6 against 5. It seems to us really difficult to do without Sage, whatever the composition. Note that she's not a simple support and leaving it to the least "skilled" player would be a mistake. The more kills you do, the faster you get her absolutely mandatory ultimate.
Brimstone: If we put aside the Stim Beacon which deserves a serious rework according to us, Brimstone has an abilities kit that is very useful in most compositions. His 3 smokes make strategising easier while his ultimate, well combined with the abilities of hils allies, can wreak havoc. The grenade will delay the opponents or force them to show themselves while causing good damage.
Breach: If Breach may have trouble revealing his full potential solo (though he's not completely behind either), he can fully express himself in premade. His kit with a blinding and destabilising abilities has no equal in Valorant to attack a BP. Finally, his Replica ability can simply one-shot an opponent without armour.
Omen: Generally poorly ranked in most tierlists, we are convinced that Omen has his place at the top of the ranking, especially in premade. His smokes are huge, you can have two at the same time AND it's his signature ability with a 30 seconds cooldown. In short, it's not impossible to use 3, 4, or even 5 smokes per round to make rushes easier for your team or delay your opponents when defending a BP. Add a flash to that, as well as a the ability to teleport and an ultimate to go from one BP to another (or the contrary to fake!), and y ou get a very useful character in most compositions.
Cypher: Cypher is a quintessential templay character. His traps and his various abilities that can reveal the opponents will give your team time to react, to correctly position themselves or to touch more easily with skillshots. Cypher is a must-have to protect his back and avoid being trapped by an opponent who tries to sandwich you.
Sova: Just as Cypher, Sova helps locate opponents. In Valorant, this information is mandatory, especially as a team. His Recon Bolt is also the perfect counter to smokes (Omen, Brimstome, ...) or Viper's ultimate. His ultimate can wreak havoc if it's well placed or at least force opponents to move. His Shock Bolt would still use a little up.
Raze: We were really hesitant about the place of Raze in this ranking. Her abilities kit is ideal for solo plays and brings relatively little to a team when compared to other agents. But on the other hand, with a team at her service, Raze can be absolutely devastating. Her abilities do enormous damage and will be much easier to place when combined with other abilities such as Sage's Slow Orb for example. Her kit is not useless either with her grenade that can easily delay a rush while your allies are repositioning or backing up, a Boom Bot that can flush out the opposing team and her C4 which can destroy Sage's Barrier or allow you to place yourself in height.
Phoenix: Phoenix is above all a character to play solo, with a rather selfish kit. His flash is especially useful to allow him to make openings but is difficult to use by the rest of his team. His abilities allow him to heal or do damage and this double possibility isn't necessarily a premade asset. His ultimate completes a generally very offensive kit and not very useful to a team. Note however that the latter can make a big difference, even in premade, in certain situations by its ability to scout opponents.
Jett: Jett is stylish, very pleasant to play and sh can shine like no other with anthology actions. Unfortunately, she brings very little to her team with her very brief smokes and... that's all. Her ability to propel herself at height and her ultimate will allow you to make THE move of the game if you aim well. All of this constitutes a fairly selfish kit which brings very little to your teammates and has few synergies.
Viper: Viper probably is the character who has frustated us the most. Her kit is really interesting with a smoke, a wall to cut the vision of the opposing team, and a Snake Bite to do damage or force an enemy to move. Without forgetting about a monstruous ultimate that can make you win 1v3 situations and defending a BP ultra effectively. But here is the issue: these abilities also hurt your allies and can become as problematic for your team as for your opponents. With good communication, Viper remains a very interesting pick in a composition.
That will be it for this ranking of agents in premade. To conclude, we recommend that you don't fall into the trap of tierlists either. Valorant is a fairly balanced game and no pick is really a mistake. A Jett or a Viper for example, will be able to shine in the good composition and with the good teamplay.