To my experience the problem is not about hacking speed or defusing speed, its the lack of aggressivness of the offensive team, which shows up on the map Shipyard, the players in the offense tend to stop in the body of the ship and try to "cover" the hacking ops from there, which is actually a complete fail, the Spec Ops is they guy closest to the enemy and responsible for the success of the mission, but he can't defend himself while hacking. As attacker and none Spec Ops your mission is to defend that guy, that means you stand between him and the defenders, to block, to make yourself prior target to buy him time, and not hiding with a sniperrifle and using the spec ops as a lure.
If the offenders would be more aggressive and block the defenders when they leave the spawn, the Spec Ops can hack close to the objective with a higher speed and doesn't need to hide. Further on the engineer has a harder time to reach the hackbox even with adrenaline and speedbuff if he is already engaged when leaving the spawn.
The problem is it takes a lot of effort to hack. You have to get multiple operatives down there to hack at a reasonable speed and then defend. Your spawn is much further away and you will have minimum one player hacking so you are defending him at a disadvantage. Slip up once in that offensive play and even a complete idiot engineer can remove your hackbox with no organized support in a few seconds. Regardless of it was a 90% or 5%. The issue is that it takes an absolute mammoth effort to hack and removing the hack is crazy easy. Thus if the skill levels of the teams are even in the same ballpark, the defense should win by default if their engineers aren't sleeping.
Compare shipyard to terminal. Terminal is biased towards defense, but people consider the offense winning in the realm of possibility because you can't reset the progress on the safe. Thus it make take 2-3 good pushes, but you get it done. Replace the engy objective with a hackbox and that mission will become impossible for the offense too.
This game is extremely biased towards the defending team, to the point where it isn't fun for the offense.