Yair said:That leaves him with only 1 daily use of his wandgrip. Normally, he uses less power - either casting spells normally, or applying the wandgrip-wand or two wands if things require more firepower. The short of it is that nothing can really withstand his firepower for two rounds.
Tell me if I a not understanding this correctly. But the wandgrip items are attached to specific items. You can change what they are attached to but I think that requires some sort of action. Thus I think your player might be doing this wrong if he is using one grip to power two wands. I am not entirely familiar with these rules but I think that holds. The question I have is the matter of wealth investment. I have looked at this build before, but discarded it as the cost of burning sooo many charges hurts the pocket book.
Since the biggest issue seems to be the fire power of the wand wielder I would suggest using monster with good SR. Due to the static nature of the wands, their caster level for SR do not go up as they level. This will quickly weaken the effectiveness of the initial burst without having to take something away from the players. For example, a few drow with about 9 to 10 levels each would have 20 or 21 sr. This means that for all of your casters they are at a 50/50 to make their spells stick, and the wands are probably worse off. Non-SR spells have one of two weaknesses: either touch attach or saving throw. So have an encounter that uses a creature with good SR and has rogue and pious templar / hexblade. A caster heavy party wont appreciate creature with SR that if you affect them they save for no effect on everything, and have at least decent touch ACs.