Brimstone works best if you have a deck that can make the most use of its Strength gain. Cards like Sword Boomerang, Twin Strike, and Heavy Blade receive the damage boost 2-5 more times than other attacks, and Limit Break can be used to rapidly increase your strength even further. Reaper also works well with Brimstone, as the additional strength allows you to regain more health.
Players who intend to face the Corrupt Heart in Act 4 will want to consider how they can mitigate the enemy strength buff, since that boss has an attack that hits 15 times. Any increase to the Heart's Strength makes this attack far more deadly, so cards like Disarm or Dark Shackles are quality pick ups. As with any build, Intangible and Weak can make the incoming damage more manageable.
Weekly Patch 44: Chrysalis
Brimstone relic buffed. Now gives the player 2 Strength and enemies 1 Strength. (was 1 Strength to the player and 1 Strength to enemies)