If you ever played with them in 5th edition, you know how the Black Rage made them susceptible to be kited around the board. It made them hard to justify for a lot of players, you had to plan around that by making sure that once they were out of a transport, they were in a position to cause havoc.
6th Edition came around, they lost Initiative 5 but gained another attack on the charge, the torrent of bolter fire is harder to resist has Feel No Pain will save you 33% of the time (5+ against anything except instant death) instead of 50% (4+ against anything but AP1 and AP2, instant death, power weapons). It's harder for infantry in general to get into assault range, no more assault out of a vehicule that didn't move. It's a bit more tactically challenging to get the charge which I believe is where the fun starts.
Blood Angels Death Company works really well as a counter assault unit with 4-5x WS5 S5 attacks per models. They will flood the enemy troops with wounds especially if they have a Reclusiarch to get them rerolls on hit and wounds. You can deck them out with AP2 weapons but the sheer amount of wounds should take care of 2+ armour, equipping power fists simply is an insurance against the volatility of dices or the presence of vehicles.
I've yet to use them with jump packs and Lemartes, they seem rather expensive for what they can hope to accomplish but in support to a deepstriking assault squad I guess they could be decent. I'm not convince that 5x DC with a power fist, jump packs and Lemartes is an efficient 350 points.
The cost is the downfall of the unit and that's why I try to keep mine as bare bone as possible for the task they are meant to accomplish, keeping that in mind will ensure you don't overkit them or try to make them do things that they aren't meant to.
