Did you try it with a non E-Tech pistol? Might be just a random case where the bonus doesn't apply because of something how the darts work or something crazy random like that. What about E-Tech sniper rifles or SMGs? I also think that 60 shots is probably not enough to make any conclusive decisions. It could be some design thing as well where the game is built in such a way that it scales the percentage so that you can't get 100% elemental effect chance (unless you hack the game (and maybe not even then?)).
 
Besides all of that BL2 is known to be fairly busted at spots when you're looking under the hood with skills not working right and stuff so might be just something like that. Bringing this up on the Gearbox forums would probably give more insight.

I haven't done any formal tests with non e-tech, but just using them in the field it feels much higher. Also, each set was 240 shots, not 60. I just broke each into 4 trials of 60 because that's how I took down my data (because a page of 240 hash marks gets unwieldy!) I haven't found any e-tech snipers or smgs, but I have at least a sniper at level 50 that I plan to test. I ran across another e-tech pistol and had very similar results, but again did not run a full 240 shot test with it.

most elemental e-tech pistols usually shoot out darts instead of actual plasma bullets/orbs/lasers that an e-tech SMG would. the initial impact can be useless but once you have a good cluster they can be pretty effective, like a Needler in Halo, if you use the elemental type against an appropriate enemy type (electric darts may not be that great on armoured but really effective against shielded fleshy enemies when you've got your electric burn and damage skills up, especially with a class mod to boost those stats.).

doing tests on the dummy isn't entirely reliable due to the fact he's usually non-armoured/shielded. sometimes the dart e-tech weapons just suck depending on the combination of manufacturer and character build.