So it's very unlikely I will ever use any of these changes - but hey its the internet so I feel duty bound to give my opinion anyway

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Land Raiders - 325pts
Seems fine for the formation with FF4+, but in reality so is 350pts. Its just there are better options in the list for what these give me as a formation.
Vindicators - 225pts
Again its fine, but again these guys are perfectly fine at 250pts with Walker, Ignore covers a great ability and they are very multi role. But again there are just better things available that I would swap them out for if I was going for maximum efficiency in list design.
Predators - 250pts Pred Dest FF3+
I prefer a split costing style and I dont think FF3+ is justified personally. But it certainly makes both Predators very good options.
Tacticals - 275pts + LR upgrade
Makes Tacticals a very good choice, personally I like Tacticals anyway at 300pts and at 275pts would definately start to use quite a lot of them. Land Raider upgrade is interesting - would probably add one to the BTS but thats about it.
Warhounds - 550pts (only pairs allowed)
OK personally I have no interest in changing Warhounds, I dont have a problem with them being very common in the list and think they are cool and fun to play with.
But if your aim is to make them a much harder choice then this would actually do it. Even if you dropped the singles or upped the cost of singles to 300pts - I would move to the pair at 500pts (and so retain the same number of Warhounds as before) for a simple reason - Its a really great and powerful choice that still gives my Marine army something its lacking. The reason its rarely seen now is because its just not quite as good a choice as 2 single Warhounds in the context of the air assault list.
Having said that I dont really care about removing Warhounds from the Marine list and the cost of 275pts per Warhound with the new dangerous critical is an accurate cost for their abilities.