At the end of the day, the answer’s pretty simple isn’t it?
When you bind your abilities, as many of them you can to keys, it can do a lot of things for you during the course of your adventures in Azeroth.
Primarily, keybinding a giant chunk of your abilities will serve the purpose of speeding up your reaction time with said abilities and, speaking as a tank, that’s definitely not a bad thing. Even if it’s a somewhat more obscure ability, one that you never use that often, if you have it keybound and are in the habit of hitting it when the situation arises, that’s something that will play to your benefit.
But like many things, there actually is a hidden cost to keybinding, even though it’s one that’s not directly related to the role of tanking.
See, the thing is, the more abilities that you bind, the more of a demand it’ll take on you to remember exactly where you placed each ability and the longer it’ll take to really get used to it and to start acting on it as muscle memory instead of having to take the time to deliberate and remember where you bound ability X.
The problems really start to arise when you start trying to shift around an ability or two. Maybe you want to experiment a bit and try to add in some other abilities into your regular rotation and you’ll find yourself feeling incredibly awkward for a while as you keep on forgetting that you’ve moved things around and hitting the wrong abilities at the wrong times.
Worse if when you spend a bit of time an extended period away from tanking, be it to spend some time with a couple two handers dealing damage or maybe even heading off to try another class or another game entirely then suddenly be forced back into the tanking role, many of us can have a bit of a hard time suddenly readjusting to the memory of the keybinds that we had.
As mentioned before, if you only have a row of abilities bound, your readjustment period will obviously be a lot shorter compared to if you were to bind almost your entirely spellbook.
It’s important to find a bit of a balance when it comes to those bindings between what you’re sure you’ll use often versus those abilities that are NOT life saving that you’ll need fairly rarely.
Making those choices early on can often make a huge difference when it comes to readjusting to your tanking skillset when you need to come back to it after a short or long absence.
This is not to say that binding a large chunk of your abilities is bad, not by any means.
Just that a little more discretion when you choose which ones to bind can be helpful over the long run.