I HATE events that tip the balance so radically. I want research, strategy, tactics etc. to be what wins or loses for me or the AI .... not "magic" events that make all my careful planning (or the AIs) suck.
Personally, I actually enjoy those balance-tipping random events. They make the game less predictable, and therefore force me to adapt, instead of just unwinding a carefully planned "winning strategy" again and again. I also don't think that random events are "magic", imho they actually make the game more realistic. In real warfare, you will *always* have unforseen events on a grand scale. Developing a strategy that is flexible enough to cope with such events is one of the great challenges of strategic thinking.
Regarding the events you mention, I found that their actual effect is less than it seems. The Ranger is a powerful ship, but it's really just one (slow) vessel, so an otherwise stronger opponent can still wreck half your empire while you are trying to decide at which of the half-a-dozen battle grounds your one invincible ship would be needed. The other event, while it certainly *sounds* dramatic, never had much of an impact in my games.
Anyway, if you don't like these random events, it should be possible to mod them out. Ask in the modding forums, I'm sure someone there can provide with the necessary information.
Side note: You should have played the first release of GalCiv 1. It featured events like giving a random civ 40+ corvettes in the early game - as player, you could really feel like single man in a dinghy, powerlesly being at the mercy of the tide of random events, which could throw you in any direction.