When attacked by Energy Damage, Bishop gains additional Power and Prowess from each attack. He can also gain this from Well Timed Blocks. But this only occurs for every Class but Tech. Techs give 0 bonus, dramatically limiting Bishop's power gain, healing and special damage potential.
While other classes have limitations and bonuses from class advantage and disadvantages, none are this severe. Black Widow's signature goes down when fighting Mutants, but is not obsolete. The same is true with Crossbones. Even Sentinels continue to gain Target Analysis from Cosmic fighters, just at a slower rate.
There's even oddities like Red Hulk, who can gain Heat Charges from blocked Mystic attacks, yet suffers no penalty from Skill fighters. Korg gains no benefit against Sciences, but loses some Rock Hard Thorns damage to Mutants (but only some, not all).
Bishop is so reliant on his Power Gains and Prowesses, and many Tech champions use energy attacks, but under the limitation it shuts down his unique ability. He and the Sentinel should be an intense matchup for this reason. Bishop requires blocking to build his specials and damage, but the Sentinel would rapidly build Target Analysis from that Mutant bonus gained from repeated moves (like Blocking Specials 1 and 2).
Even the artwork posted when Bishop was released seemed to imply he would be useful against Tech's:

Bishop's Tech Disadvantage just seems greatly off when compared to other designs. Maybe reworked to give only one Prowess across all classes on Well Timed Blocks, and two on energy attacks (with three from Well Timed Blocks), and six from energy Special Attacks (boosted to nine if hitting a Well Timed Block). This would make him gain much less from a strictly Physical Fight, which should be his limitation, but rapidly jump him in an Energy Heavy Fight.
Keeping his class ups and downs more in line with other fighters would make him a better appreciated fighter.
He also needs his Synergies reevaluated. The only outside synergy available to him is the Nova one, and the others he has are too similar, except Chronal Anchor...which is underwhelming.
Storm is his protective grandmother in the future, his team leader in the past, they should have some special Synergy that's more than power/prowess to start and some energy shielding.
Gambit is also involved in his different timed lives, yet neither have a connection in the game.
Cable and Bishop are both time travelers who seek to change the world from horrifying futures - there should be some connection.
Cyclops' connection could be reference to the Summers Rebellion, which worked to free Mutants from enslavement from Sentinels, and even the Sentinel and Bishop could share Synergies that reflect the Subjugation and Liberty each represents in that future.
Chronal Anchor would be better if both he and Psylocke also gained the Percentage of Power and Health they prevented on their opponent in that lockdown.
It's also worth noting Bishop was part of the XSE, the Mutant police force of the future. It might be useful if he gained some bonus when fighting Mutants, since he's experienced in having to police them.