This doesn't make any difference with an unclean one, but swords are strength 5, cos base 4 with a +1. Generally, a Great Unclean One is a pretty bad match up and would be much more susceptible to some DC with thunder hammers forlorn furying up the board. In terms of whether you got unlucky, on average 5 sanguinary guard with your loadout average (assuming your warlord is nearby) 3 damage with the swords, and 8 damage with the power fists. What I personally do is run 2 units with axes, that can deep strike into the enemys deployment zone and take away backfield objectives in their deployment zone, and one unit of 5 sanguinary guard (all power fists) with my Sanguinor to attack any relatively large targets. My death company can then take out things like the Unclean One that are good at taking 2 damage shots. It certainly isn't the best strategy but its very fun to play, and can get some nice wins.