i have a question about michizures effect which is

you can active this card when your monster is sent from the field to the graveyard. destroy 1 monster on the field

so does this mean you can only activate it in a turn a monster of yours is sent to the graveyard?

I't dosen't matter whos turn it is as long as you send a monster to the grave yard. so scapegoats will not count. It could be your monsters effect or your opponets. It could do quite well in a deck with limmiter remover or wild naturwes releace.

I think Michizure is a good card. To activate it, it doesn't matter how your monster was sent to the graveyard (you tributed it for another monster, your opponent destroys your monster in battle, etc) and you get to destroy 1 of your opponent's monsters (BLS Envoy, BEWD, Dark Magician of Chaos, etc. except for Jinzo).

Do take into account though, the fact that a monster being sent to the Graveyard MUST be the very last thing to occur in order to use the effect of Michizure. So, if you Tribute a monster as a cost to activate a card, you can't activate Michizure, if you Tribute a monster for another monster, you can't activate Michizure, if your monster is destroyed as a result of battle, you can't activate Michizure (because you're in the Damage Step), etc. If the monster is destroyed by something like Raigeki Break or Tribute to the Doomed, etc., then you could activate Michizure because the last thing to occur was the destruction of your monster, and subsequent sending of it to the Graveyard.

Michizure is now another card ruined by that optional rule

Michizure has always worked that way (infact all cards work that way if they have timing requirements). Players can never activate an effect that has a specific timing requirement after that thing occurs.