Basically, the extra Disc from SoJ is additive, and Bastion set is multiplicative, not just with the Disc bonus, but with each other, so Bastion will always be better.
As BlackcurseLT said, if you're going from 85 Disc to 95, you're changing the bonus from 8,500% to 9,500%, but if you use the Bastion set, you're going from 8,500% to 19,125%, with both buffs active.
Even if you include the damage to elites and elemental damage from the SoJ (assuming you have none from any other source) the best bonus you could get is 14,820% - and you have to remember that by using a SoJ you're also sacrificing CHC and CHD which will severely nerf your damage too.
It's simply impossible for any SoJ build (even combined with Endless Walk) to compete in damage with the Bastion set.
If you find your toughness is too low then you can switch to the Endless Walk set (Traveller's Pledge and Compass Rose) and then use both Convention of Elements and Elusive Ring. It will increase your toughness considerably, but will lower your damage compared with Bastion of Will.
At the moment I'm using Elusive Ring instead of Convention of Elements, mainly because I find CoE to be too unreliable. While the damage from CoE is very nice, the toughness from Elusive Ring is too good to pass up, especially since your damage while dead is 0.
Rollback Post to RevisionRollBack
And may the odds be ever in your favour. Emmo#2406