You can Normal Summon this monster with 2 Tributes as well.
"You can Normal Summon this card by Tributing 1 "Gravekeeper's" monster" is not an effect.
If a "Gravekeeper's" monster is discarded to prevent this monster from being destroyed by battle, you perform damage calculation with the ATK of "Gravekeeper's Visionary" without applying the extra 200 ATK.