Your choice of Tier 6 talent comes down to encounter play style requirements.
Elemental Blast - Stationary or fairly low movement. More consistent DPS. Better for target switching.
Primal Elementalist - Mobile DPS where the target is not moving. More bursty DPS. Falls behind EB and UF for single target in 5.4, but pulls ahead for cleave (2+ targets) fights.
Unleashed Fury - Mobile DPS where the target is moving. More consistent DPS. Currently the strongest on pure single target. However, because this applies as a debuff to the target rather than a buff to the caster, EB will pull ahead when target switching is involved.