I get what you're saying, but... I gotta agree with Rongway. This is the reason tanking for pick ups is stressful. This is why there aren't more tanks. While you may perhaps believe you are an attentive person there may be things you don't know and the majority of DPS won't stop themselves before pulling the boss. Fresh into a dungeon with 3 random strangers I don't know you. I don't trust you. I have to assume you're going to make a mess and that you have no self control. I don't save the DPS who pulls for that person's sake. I save him for the party and the rest of the group's sake. The healer will probably try to save the guy that pulled or the other DPS may jump in and then it's a bad time for everyone. So I'll be a good sport about it and intervene but too many runs like that and I'm exhausted and done for the night.
If it isn't a fight with a tight DPS check, no, I'm not going to stop for a countdown. I'm going to keep that momentum going and I'm just going to run straight in. Unless of course I need to stop because someone's AFK, mana, buffs, or I'm typing because I have a question about the boss we're about to fight.