Why do some spells like Hell's Core and Ultimate Energy Strike have a longer group cooldown (4 seconds vs 2 seconds)?

Question

When attacking with most instant spells and runes, the game imposes a 2-seconds cooldown before you can attack again. However, some strong spells that have high secondary group cooldown (so can't be used very often) will trigger a 4-seconds cooldown. In some cases this make players avoid using such spells at the beginning of a fight due to the extra time off.

Answer 1

Hey, for example with an ava you can reach 500 hit, with the UE you will probably reach more than 1500, so it makes sense to have a higher cd. The earth UE is shit, but the others, taking into account the weaknesses of the monsters you are hunting, are very useful.