Actually i think a wolf guard unit costing only 235 points would be eaten alive by a 5 th/ss + cyclone unit. Wolf guard have to pay 15 points for each storm shield making them very expensive
As for fearless I don't agree with that at all, almost every time i play against marines i make their units flee at one point during the game, and if you have fast units to follow them off the table they keep on running.
A battle i had not long ago i followed a starting unit of 10 th/ss terminators of the board with a tau drone squad. And they were in charge range of my entire line and would have wiped me the next turn had they not braked.
In assault it may kill a terminator from time to time, but i hardly loose with my terminators in assault anyway but against shooting it's nice to never have to take moral tests, especially against imp psyker battle squads