So, maybe I just haven't been playing Netrunner enough, but Wyrm seems... Lacking?

In order to interact with a piece of ice, you need to be of equal strength, correct? It can decrease the strength of ice, but only after matching it's strength, either by paying up, or using Datasucker/Parasite/etc. My biggest concern, it costs 3 credits to break a single subroutine, and only on ice of 0 or less strength. So my question: How does one effectively use Wyrm?

You definitely should not use Wyrm to break subroutines. The idea behind wyrm is that it is one of the only programs in the game that can uncoditinally lower the strength of ice. Datasuckers require open centrals to load up but if they get wiped and the corp locks you out of their centrals? That's ok you've still got Wyrm. Again you do not want to use the Wyrm to break the subroutines instead you want to bring down the strength of ice so that fixed strength icebreakers (atmans yogs mimics etc) can break the ice itself. Also it could come in handy to destroy ice with parasites. I don't think anyone would argue it's a great card but I've seen it used in a pinch to make it work.

There's actually an ICE destruction archetype, based around parasite recursion, and some versions of the archetype use Wyrm rather than Datasucker to achieve this.