Let's see... if he drops the thrown weapons idea, he could put the Explosive Runes on a bunch of parchments, roll them up, weight and bind them (for ease of throwing), have them tossed into the opponent's square (possibly by having a bunch of them in a bag, and tossing the bag, open, at the square), and detonate them with dispel. They are on a writing surface, they are thrown at the square (not the opponent), they are unattended, they deal Force damage, there's enough of them that even with a 50% (although... if you make the ER's, and you cast the dispel, you roll 1d20+your caster level vs a DC of 11 + your Caster Level ... in other words, 1d20 vs. 11 - a 50% chance, exactly, until you hit the caps on the caster bonus for Dispel (10)) "fail" chance, some of them will go off. If you put 10 of them in the bag, five are likely to go off, and deal 30d6 force damage, reflex half (5 reflex saves, for half of 6d6 each) to everything within 10 feet of the bag.
It's more useful as a trap in a fortress - you have cheap maps, tapestries, books in display cases, et cetera, that have ER on them in non-obvious places ready for that Area Dispel.
Edit: Let's see... a sheet of paper is listed in the SRD for 4 sp; 20 of them would cost 8 gp. A basket to throw them runs 4 sp as well. 8 gp, 4 sp, and 10-20 days preparation for 60d6 force, reflex half, at 5th, in one round? Nifty!