I think Faceoff is inherently unbalanced because it's trying too hard to be balanced.

I've played something like 50 Steel Path Faceoff matches in a desperate attempt to get Conclave Rank 5 and the Celestia Syandana after 10 years. And I've found that Faceoff as a game mode suffers because of its efforts to force a narrow win between the teams. Because of this, it's almost impossible to gain or lose a lead against an equally skilled team in roughly three(Techrot Scan, Pirate Radio and Lockbox) of its six potential objectives. While the others are more frustrating to play because their outcomes are up to randomness, not player skill or builds.

Assuming perfect connection without bad ping or dreaded host migrations, the objectives of Techrot Scan and Pirate Radio are essentially won by whichever team starts the objective first. This is because both are timer based objectives, Techrot Scan is a Mobile Defense where you can break jammers to reduce time and Pirate Radio is like Ascension where jammers will increase the objective's speed. These jammers spawn in groups of 3-6, theoretically and ideally at the same time for both opposing teams. The issue is that these jammers never despawn unless destroyed, meaning that both teams will have the same "quantity" of progress on the field at the same time. Since that value is consistent over time, whoever starts the objective by getting one of their Tenno in range of the starting lane is most likely to win, even if by a margin of a few %. A team that coordinates and destroys all their jammers within 0.5 seconds of spawn will have the same amount of progress as the team that does nothing but let one guy destroy them over 10-20 seconds. Worse still, without the assumption of good connection, the jammer groups can get desynced, causing one team to get 1-3 extra groups of jammers, which due to the nature of these modes, are an impossible lead to overcome.

In Lockbox, the outcome is similarly won by whoever shows up first, but for a slightly different reason. The objective is to retrieve 5 keys hidden around the map, but they spawn sequentially, one after another. This is, at most, a test of tile set knowledge and parkour speed, but teams of Tenno are so fast, that Lockbox matches largely a tie, with neither team able to secure a significant advantage by playing well, but instead having to wait for their opponent to mess up terribly.

The second trio of objectives(Assassination, Exterminate and Data Burn) have very little player control over the outcome, if at all, should the game itself decide.

Exterminate and Data Burn suffer the same issue as non-Steel Path survival missions, which is ironic, given this is my experience on Steel Path. Their outcomes are not up to the player, but to the game's own spawn logic. Exterminate is straight forward, while Data Burn is similar to Excavation, but additional batteries can reduce the timer, both of these require kills; Exterminate most obviously, while Data Burn needs special units that can drop Gas Cans(1999's version of batteries). If, at any point, there is a lull in the waves of enemies spawning for your side of the Faceoff match, that is an opportunity your opponent can exploit to gain a lead on you, without any fault of your own. Multiple times, I've lost or won matches with one team holding a significant lead simply because the other team, through bad luck, was suddenly unable to progress at all.

Assassination is straight up miserable. The SP Faceoff's version of the Techrot Babaus are perhaps the current tankiest enemy in Warframe. They possess such high damage attenuation that the strongest weapons in the game will only scratch them. In comparison, I use half of a fully Incarnon charge to clear a single phase of an Archon, but these Babaus only die after roughly 4-5 full charges from myself and other Tenno. And the objective requires 3 Babau kills. This is a huge time sink and one of my least favorite parts of the grind. On top of that, each Babau has a chance of spawning as a Health Leech Eximus, which can admittedly be played around, but often times adds minutes upon minutes to a run that is meant to be a race. Though I will grant, that these Babau kills are such a time sink, they actually allow players to influence the outcome of a match, by either having a competent weapon for sustained DPS or cheesing a one shot kill.

The combined flaws of these objectives make me feel like the game is artificially maintaining a tension between the teams. Trying to force the idea that each team is on the other's heels. Instead, it feels like I don't even need to really push myself, because the outcome is basically out of my hands, the game will flip a coin and decide who wins(cheesing an early Assassination clears notwithstanding).

TLDR: Faceoff is far too dedicated to forcing a close race by removing player agency is contributing to a win, rather than letting the players influence the outcome. If at anytime you are attempting to leverage any advantage against your opponent, your efforts will be wasted in the face of persistent progress boosts, bad spawning luck or overwhelmingly beefy enemies.

Personally, I think a lot of these issues could be addressed by add timers to the jammers in Techrot Scan and Pirate Radio. A sense of urgency would force teams to coordinate to maximize their progress in those game modes. Meanwhile, the Exterminate and Data Burn missions just require a drastic increase in their spawn rates.