Eirene isn't used as much because it's been sold once by the gunsmith in a foundry package (which most people neglect), but it's limited use is not an implication that 1000 yard stare (which drops from vanguard packages / can be bought any time / is a reward from a quest) is overpowered. Now that I have an eirene in a week I'll probably use both depending on the rolls that come out