Looking at your chart you have 11 events: 5 do nothing, 3 have the chance to kill agents, 2 technically can't be used until they are translated between games, and the last one can be useful - if the situation arises that the skill can be used.
I humbly suggest that is is one reason your agents get bashed about so much, as there is almost nothing there to help the agents during a game.
These aren't event cards, they are randomized results of searching certain artifacts placed throughout the terrain. I do not want every artifact to contain a game changing result, that is why half the results are "do nothing". As for the magic spells, they are deemed useable as soon as they are found. As for the zombies.........well..........I like zombies.