I think your approach to this is completely fair, but as a shield main I want to give my opinion on why I don't agree with this suggestion

Shield pvp is often seen as no skill PvP. I understand that view, but I think it's incorrect. On CCNet you have 4 type of PvPers when it comes to using the shield

1. Good shield user, good pvper = great combination
2. Terrible shield user, terrible PvPer = qd
3. Good shield user, terrible pvper = qd when shield gets disabled, but uses shield well enough to hold themselfs off for most of the fight
4. Terrible shield user, good pvper = Shouldn't use a shield, it only weakens them

Players 3 & 4 are the point I'm trying to make here. The shield isn't some sort of strenght 3 potion you use and now you're suddenly better. It's a tool you need to get skilled at in order to use it properly. I've seen some PvPers that completely destroy me in normal pot PvP, but when they attempt using a shield, it all falls apart and they got no clue what to do anymore, but if shield was no skill, shouldn't those great PvPers be only getting better?

Imo shields are hard to actually use properly. Timing the deployment of the shield, and then lowering the shield to get a hit is very difficult to do perfectly, and often when mistimed, it can bring you in an momentum where you keep trying to get deploying & lowering in an attempt to get the timing right, just for you to get critted out completely. And because when you use shield you stand still, having a messed up momentum like that, can often lead to getting quickdropped, or being forced to pot while your enemy is next to you (they get healed too)

Lastly, I believe most people who dislike shields or want them nerfed just refuse to use the axe. I recall olpx used to hate on shields because I was able to kill him because of it, but then when I rewatched our fights, I sat there for multiple seconds, holding my shield without him ever hitting it with his axe to disable it. And now a days, where the cooldown is 8/9 seconds, the value you get out of it is huge. If you ask me, it's your responsibility to counter a shield, it's not the shield user that needs to get nerfed, it's the value that a shield counter gives, that should be buffed. Hence the increasement of the disabling the shield from 5s --> 8/9s

Having that said, I guess the crit axe hit adding 50% would comply with what I just said, but I still think that'd be to devastatingly long, so I would say like 25%.

Ever heard of an axe?

Yes sumo, I hear of axe. That's why I want to change something about shields and not to remove them.

But for people that have high ping it's almost useless to use a axe since it's very difficult to disable shields at the ms.

And for people with high ping it’s almost impossible to combo effectively without a shield. You are also making it so that getting hit in Ganks is a 100% death rate. At this point you might as well just say you hate shields and shield pvpers.