Not meaning this to be as snarky as it will probably be...
But you were trying to hit them yes? Dropping a shield is better then passing, because it removes a card, puts up a defense and doesn't cost you a pip.
It will not be the last time you see a shield wall. Wait until your fighting three ice and a life mage. The life mage will have a double thick wall of tower shields so the life mage can focus on making sure the rest of the party stays alive no matter what you do.
Sounds to me like they were using good strategy. Here are some ideas for dealing with it; try a few and see what works for you. Carry a wand of your school or your teammate's school so you can knock out a shield without wasting a pip. Carry a few one-pip spells of your first or second school to knock down shields right before using your bigger attack. Bring along some treasure cards called "Steal Ward" (find a friendly ice mage who will make some for you) and you can remove the very last shield placed and put it on you instead. Use multi-hit spells like fire elf to keep knocking off shields. Ask around the commons or places where people trade treasure cards for "mutant" elf cards (storm elf or ice elf) that do the same thing for the other elemental schools. Rely more on blades and less on traps since your traps will get knocked down at the same time their shields are. Make sure someone on your team has an Earthquake treasure card, and when all of you have saved up your pips and have your attack cards in hand, use Earthquake to clear all the shields at once and then hit with everything you've got.
Everyone who does PvP for long ends up having to learn how to deal with shields. Hang in there!
That is a common stratagy, mostly learned through pvp or dragonsypre's shield master ( boss that has 2 helpers and all they do is shield and a rare attack ) .
But i always have a trick up my sleave, my steal ward is most useful. I will be in pvp and a noobish life wiz will use absorb and think they are now invincible, i just use steal ward XD. Even better i was in this one battle with a low level ice wiz, she saved up all her pips to cast a big ice armor ( absorb per pip ), and i just used a steal ward and all her work was gone.
Best thing to do is to get the DS hat that gives earthquake, stats are ify but earthquake is well worth it.
if you're Myth, once you get earthquake and Orthrus you can laugh really hard at people who put up shields against you (not to be mean, but you really can't defend against Orthrus.) Death, Ice, Storm, and Fire have dot spells for shield removal(storm needs stormhound for their dot though). Life, on the other hand, just needs to hope they don't deck out after using up their attacks breaking all the shields(sorry you life wizards out there :-() Finally, balance has hydra as its form of shield removal, but IMO life REALLY needs some type of shield removal; even the teachers seem to realize that life has trouble breaking shields on its own as no npc opponents seem to ever play life shields.