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you can in fact use warp blast if you have enhanced sences. you just cant use the concentrated blast that is s10 ap2. you can fire the s5 ap3 blast template while equipping your tyrant with enhanced sences.. i see ALOT of people thinking theese 2 powers are mutually exclusive pg 31. tyranid 4th ed codex states "Atyranid with enhanced sences may not use high powered bolt.." refering to the s10 bolt .. not referring to the entire power.
I think a lot of people already knew that, but there are better alternatives out there than a small blast template that misses 1/3rd of the time. For instance, two sets of Twin-Linked Devourers are still better for killing marines, and massivly better for killing things with lower armour saves. That, and taking the Warp Blast prevents you from taking a more useful psychic ability, such as Warp Field or Psychic Scream.
While you can still use the unupgraded version of Warp Blast, you wouldn't want to. There are better things out there.