Looks like Mythic will be changing the current way that auto attack haste works in Warhammer. The following is taken from the offical forums:
There’s been some heightened concern regarding Autoattack Speed modifiers recently, so we’d like to share one of the changes which will be in patch 1.3.5. We’re adjusting the manner in which these modifiers are calculated to bring them back in line, while still ensuring that they remain useful and valuable.
Currently, Autoattack Speed bonuses are a direct modifier to your swing time; for example, a 50% bonus would literally reduce your swing time by 50%, resulting in twice as many attacks (or “100% more attacks”). Instead, these modifiers are being changed to affect the number of attacks – in other words, a 50% bonus will now give you 50% more attacks. By the same token, please be aware that the numerical values of Autoattack Speed -debuffs- have been reduced as a part of this change, but this simply ensures that their overall effectiveness remains unchanged. As an example, a “50% debuff” would previously have resulted in the victim getting 33% fewer attacks, so it will now simply be displayed as a “33% debuff”.
I know that this is a “math-y” change and can be a bit unclear, so let me provide a quick example which may make it more understandable. Let’s say you had a weapon with a 3.0s swing time, and you had a 50% Autoattack Speed bonus. Previously, this would have given you a 50% reduction in your attack speed, reducing that 3.0s to 1.5s (or twice as many attacks). After this change in 1.3.5, that same 50% bonus to your 3.0s weapon will give you 50% more attacks, which will reduce your swing time to 2.0s. Likewise, a 75% bonus would previously had reduced a 3.0s speed down to 0.75s, whereas after the change, it will give you 75% more attacks (or a 1.7s swing time). As you see, this isn’t a -huge- change, but rather a very targeted adjustment which brings this bonus back to a level that we’re more comfortable with.
Going forward in the future, we plan to individually review all abilities, tactics, items, etc. which grant Autoattack Speed bonuses, and determine whether their specific values are appropriate. This change is a necessary first step before we drill down to that level of detail, since all the spot changes in the world wouldn’t help until the underlying system itself was fixed.