Obfuscate is a neat Discipline and useful in many situations, but for role-playing rather than roll-playing reasons I think that some things needs to be fair.
Rolling for going invisible after getting that 4th dot in it, seems pretty meaningless when outside of combat. Without a doubt it will eventually work, so for those times when it is not inside of combat. Fading can be done and assumed to succeed, there is no point in rolling for it 20 times until it succeeds with everyone.
When getting the 3rd dot, a Mask of a Thousand faces which the character is familiar with. Can get an automatic success, all though it is going to be marginal (it will count as one success). Mask of 1K faces could also be used to raise the Appearance trait temporarily, for every success you score if you decide to take the roll. Your appearance will be considered to be +1 until you drop the mask. Furthermore you will need Obfuscate 4 before you can apply a Mask of 1K faces in front of people, granted it is still a Masquerade Breach if it's with humans.
Spotting someone who's Obfuscated: If someone walks around invisibile and you have your Heightened senses on, you may be able to spot someone in hiding. However, you will not become aware of it due to the wake it creates when you walk around in a crowd hidden. If you have your heightened senses on and have a higher Auspex rating than the hidden one has Obfuscate, you will automatically see through the Obfuscation. If the Obfuscater has a higher rating, it will be impossible to notice him or her. However, if both have the same values the Auspex user will roll Perception + Empathy difficulty 7 vs. the Obfuscater who rolls Wits + Stealth difficulty 7. The one with the most successes wins and in case of a tie, the Obfuscater will not be revealed as in this case it will be counted as the 'Defender' for rules purposes.
This also means that someone with Auspex 4 or 5, will be able to see through the mask of 1K faces of someone who has an Obfuscate rating of 3, it is not just the fake invisibility that is effected.