Guild Wars 2

Extended potion (1 hour)
+10% damage vs <specific mob>
-10% damage from <specific mob>
+10 Experience from kills
Recipe bought with dungeon tokens and soulbound on acquire.

Powerful potion (1 hour)
+10% damage vs <specific mob>
-10% damage from <specific mob>
+10 Experience from kills
don’t need recipe and it’s trade-able.

Why should I ditch 400 dungeon tokens for a recipe that make soulbound on acquire potions when I can make powerful potions? Is this a bug?

extended lasts longer.
Which is pretty darn useless. If you need the extra time to finish the dungeon (which is just about the only place worth using the potions) then you’re probably dying, which ends the potion anyway.