Time dilation would be good but the only downside would be Rudra INT points. Becuase if he hasn’t leveled up since the last time he met Hades then that means he has 14500 INT points (14500 points equals to 145 seconds of invulnerability, not full 3 minutes).But with the incoming 80 levels and 3000 stat points our boy would probably reach 20k int points which will allow him to have 2k left for whatever moves or skills he needs to use. Although the current Rudra would not be able to use much moves after time dilation, the latter Rudra would be able So time dilation would probably be his greatest choice as it would be his trump card for when he goes up and face gods and demons. And when he is in tier 5 he probably have enough INT points to use the skill without any drawbacks.

Hypothetically, if Rudra had chosen the death legion skill, would it be able to summon tier 5 elder liches?

What a mad lad. Knew about the future