We've got just what you need to add a touch of Mythic to your brutes and soldiers-- the Achillean template.
This is part 1 of 3, and sure to give your monsters an unexpected twist, providing a nice combination of mythology and template mechanics.
-Ben.
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Small but Fierce.
Kobold Quarterly's News Minion.
Cool template - but keep it as rare treat unless its being put on a big bad for which there is a Mcguffin available in a previous adventure.
All those resistances will turn 4E's many round combats into some combat that takes a phenomenal number of rounds. That is OK, especially in a good boss fight with some interesting scenery and other stuff going on in the background but should be avoided like the plague in a throw away combat since a fight like this will eat up most of a nights gaming - fine for an adventures epic fight but not so much for room #2 of the dungeons upper level.
The other rather tricky element here is that few powers have special types of damages associated with them. Characters that use arcane magic usually have such powers and divine type characters can usually do radiant and may have some encounter powers with thunder or fire or what not but most characters can not easily attack the enemies Achilles heal even if they happen to know what it is unless the DM provides magic that allows them to do so. Hence such an encounter should usually be chosen carefully and acts to really put one the groups arcane spell user into the spotlight. One could also highlight the divine type characters by making the Achilles heal radiant but its probably a waste - such characters get this type of reward every time the party fights undead creatures so making radiant the vulnerability won't seem all that special - and this encounter should really be special.
Special thought regarding the scenery and a well designed encounter can be a big help here...if there is some way for the other characters to get their hands on the Achilles heal in the scene itself (preferably a way that is not super obvious to the big bad but is clear to the PCs (maybe they have insider knowledge)) this could allow the party to work to try and accomplish a bunch of divergent goals - help the mage keep the damage up, defend the mage, and accomplish the the tasks necessary to introduce the Achilles heal into the encounter. Done well such scenes are really rewarding to play (easily some of my favorite 4E scenes involved this sort of thing) but they involve significant DM preparation and forethought.