I disagree with this.
You're saying the REAL problem is the slide -> jump. First, sliding speed is fine - you dont feel like you become flash, it doesn't have a large distance, you can't aim down sight, you get a penalty after sliding, the only real benefit is changing your level (height) and keeping your momentum. Jumping gives you a significant penalty to your accuracy. Jumping from a slide allows you to keep that momentum but you get penalized significantly.
Combined, yes that makes a target much more difficult to hit but you get so many penalties that the person shooting you shouldn't be killing in most scenarios. Your accuracy should beat their movement. Im not quite sure the magnitude of spread you receive but it is significant.
Slide being used offensively is great but isnt always the best option. In most cases its used to round a corner or behind cover to finish off an enemy who was already hurt. If you round a corner with a full hp enemy you usually lose those gunfights. So a offensive slide isnt OP or anything imo.
Possibly what it boils down to is your skill and ability to hit a moving target. Ive only been killed once by someone using that movement in a close range. Otherwise my positioning and gun skill out perform their hyper-aggresive movement.