small pumpkin man
Explorer
This was a very good argument, one I subscribed to myself, at least until the Swordmage came along. Most of the Swordmage implement powers do still confirm to to this, and shouldn't get such bonii, but specifically powers like Corrosive Rain and Lingering Lightning break the mould.You are stretching the rules. If you're DM allows you to get away with it, then no quote here is going to help.
The Swordmage mechanics allow you to use a sword as an implement. When it is being used in that fashion, it is weapon, not an implement. You get neither the Weapon Focus bonus nor the proficiency bonus to hit.
Look up the warlock pact blade in the Player's Handbook. It very specifically indicates that you do not receive the proficiency bonus on attack rolls when using a pact blade to make implement based attacks.
This is an indicator that the game designers intended for implements and weapons to function seperately even when a weapon is both an implement and a weapon. The Holy Avenger is set up exactly the same way. You neither receive the proficiency bonus to hit or any bonus to damage roll bonues that apply to the weapon or melee based attacks because the Holy Avenger is being used as an implement, not a weapon for powers with the implement keyword.
For you to try to apply weapon focus to implement powers is you trying to stretch the rules for every little bonus. Weapon Focus is bonus damage for a weapon. An implement is not a weapon, it is an implement. You don't receive either the proficiency bonus to hit for the weapon or any bonus damage applied to the weapon. That is the rule. It is all over the Player's Handbook. Look up Holy Avenger and Pact Blade. And look at the rules that specifically state you get to use your sword as an implement as well as a weapon.
Why would it even bother to state that the sword could be used as an implement if it was both at the same time? 4E was very careful about delineating between the two. You should be too.
These Powers which have the implement keyword, not the weapon keyword, but which use weapon dice anyway, confusing the whole issue, since you're obviously using some property of the blade as a weapon, not just as an implement, so do you get Brutal or High Crit, if not, why not? These things are part of weapon balance, so arguably they should be there, but it's not made obvious, and you're very specifically making a weapon damage roll, so why wouldn't your feat which grants bonuses to weapon damage rolls work?
It's not straightforward and it's not simply laid out.