The Issue: The PvE Serendipitous Assault (SA) relics do not stack with the PvE Direct Damage (DD) relics (Dark Radiance, Elemental Transcendence, etc).

Details: When the PvE SA relic of any tier procs its power buff effect, it puts any equipped DD relic on a 4.5s cooldown. The same happens the other way around. I would not expect this to happen because the relics are only supposed to be non-stacking with similar effects. Their effects differ in the following ways:

• Trigger - The SA relic triggers on damage and healing, while the DD relics only trigger on attacks, both at a 30% chance.
• Damage Mechanism - The SA relic applies a 6s buff on the user that increases power, while the DD relics deal a set amount of damage directly to the target.
• Cooldown - The SA relic can only apply its effect once every 20 seconds. The DD relics cool down in 4.5 seconds.

As it is now: Currently, the SA and DD relics used together cannot proc both of their effects within the same 4.5 second period. Upon browsing a combat log of a long parse, the effects are always separated by 4.5 seconds.

If it worked correctly: The relics should be able to stack, which would mean the effects of both relics should be able to proc on their own cooldowns independently. This would keep the SA proc from being delayed by multiple DD procs in a row and allow DD procs on top of SA procs as well.

What this means: As it is now, a player using both relics may as well be using just one of them, if not for the static stats on the relics. The inability for these relics to stack decreases potential DPS by 1-3%, depending on the RNG.

I've been trying for a while to get Bioware's attention on this issue, but have not gotten any response from them nor support from players in any of my attempts. I have submitted 2 bug reports in game, and five forum threads that have gone completely unnoticed by devs and players alike in the Customer Service, Suggestion Box, General Discussion, and the new Bug Reports forum.

UPDATE:
Combat logs from parses with PvP and PvE gear.

Carnage, PvP, SA, DD http://www.torparse.com/l/242155 Power Surge is the SA buff, Wind Buffet is the DD attack. In this short PvP gear parse, you can see the Wind Buffet proc'ing within 4.5 seconds of the Power Surge effect twice (Second Power Surge), once before and once after. It procs 3.2s before and 1.4s after the Power Surge.

Annihilation, PvE, SA, DD http://www.torparse.com/l/242323 Power Surge is the SA buff, Dark Spike is the DD attack. To browse this log, it is best to ctrl F and search for Power Surge, then look within 4.5 seconds of each one front and back. The fight lasted almost 5 minutes, but not once does Dark Spike proc within the 4.5 second frame before or after a Power Surge.