As has been noted elsewhere, the Hands of Stone DC is much lower than expected from the description.
The tooltip DC is 10 + Constitution Modifier + Character Level. I've been doing some testing with it, and cannot seem to find what actually modifies the DC.
Caster: Dwarf, LV14, 10 rogue/4 artificer
Expected DC based on tooltip: 33
Testing results: Failed to save on 20, saved on 22.
Ok, so the DC is off by 11-12. Simply dropping one of the modifiers from the equation won't solve the problem (modifiers are 10, 14, and 9).
I try dropping CON to 25.
Testing results: Failed on 20, saved on 22. Edit: Save on 21.
So no change. How about DEX (8+14, DC of 22)?
I drop DEX to 21 (5+14, DC 19).
Testing results: Failed on 20, saved on 22.
Once again, no change.
All right, let's try a different level.
Dwarf, LV7, Fighter 7
Expected DC: 23
Expected DC from previous test: 14-15
Testing results: Failed on 8, saved on 10.
And I officially have no idea what's going on here.
Note: My apologies lack of definitive DCs. Testing this SLA is a pain with the cooldown of 30 seconds, the charges limited to 4 per rest, PvP pits disallowing the SLA, and PvP arenas not resetting charges until death. X(
Edit: Additional tests were performed with a LV21 Dwarf Wizard. A possibility suggested by a guildie was the DC might be Level*1.5. However, the test results for the LV21 indicated a DC of 25-28, rather than the expected 30.