This change is trying to do 2 things. It guts fizz use of ultimate because players don't read patch notes and whine that the hitbox is broken because they still haven't figured out that it had an increased latch on range. The second thing is to try to introduce a new mechanic, the numbers buffs are insignificant and the W buff actually nerfs the ability's damage, especially early.
By increasing the duration to 6 seconds they're trying (Though I could be overestimating riot's thought process) to make it so fizz can proc the mark, use an empowered W then beable to wait around and beable to use his W again before the duration ends without having to stick to the target and reapply the mark with an Auto.
Issue is that the window is too short at only about 1.5 seconds with just the W>Q but less than a second if you need to wait for E. And if you're walking around at the only distance you can sit at so you don't die then this window is far from enough, especially if the champion has a mobility spell to get out of your dash range or even just dodge your Q. Because ya know his Q totally fun being dodgeable. All the while you're doing this though you'll have the ADC, midlaner, and most like a melee carry, bruiser, tank or something else riding you and either killing you off or preventing you from getting anywhere near the enemy you're trying to kill.
It's REALLY like they're just trying to make fizz build tank so they can nerf him again in order to put him in the lowest possible point they can accomplish.
Though this is still under the assumption you can somehow apply the first mark without getting one shot if you're going melee or somehow land the ult that they're trying to gut and punish players for using at a distance.
