With the new cave generation, I think that the pillars are somewhat a bit weird. I have 2 things to say:
If the pillars are not working as intended - Well then that's a bug
If the pillars ARE working as intended - These pillars are awfully long, and maybe the generation of mineshafts can change a bit.
Read the Snapshot change-log. It's a feature for Mineshafts to suit the new cave gen.