For crits, use the command addcond 11 (at least I think it's 11). However, this requires cheats and a point_clientcommand entity. As for overheal and other advanced effects, I think you need SourceMod on your server.
A trigger would send an input to a point_clientcommand, which would then add crits to the player, clientside. This could most likely be exploited, so I suggest just using SM.
When I send the input to the point_clientcommand, would the 'addcond 11' go in the override parameter box?
(Sorry, I'm relatively new to mapping)
EDIT: Nevermind, got it. Thanks.
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