Something needs to be done about Fioras Ultimate.

use zhonyas

Play Master Yi with cleanse and max W first. Try to bait her into diving you with her ult. If she ignites you before she ults you, just cleanse it then proceed to meditate through her ult. Then just kill her. You outscale her and honestly after you get the first kill on her she is no longer a threat to you and you can just keep killing her over and over.

Kill her before she ults... silence her before she ults... stun her... walk outside the radius so that she isn't life stealing from everyone... trash her in lane so the the ult only tickles... lots of counterplay there.

The first and last hit are always on the same target. Use the fact that she cannot control where she will end up after her ult to put her in a bad position.