Are u sure?
With ccminer 1.8.1 it make 250mhs each on LBC (with default clocks).

I get similarly bad results with 1060, and 970.  They don't do well dual mining LBRY.  Dual mining SIA they are ok, but more profitable to min LBRY only with ccMiner.

with CCminer I do 375-400MH/s on my GTX1080 :-D
Tomorrow i will get a RX480 ...lets rumble.

Have you heard the news about SIA and LBC fund raising?

When LBC has more profit than ETH, better mine LBC only. But if LBC has about same profit as ETH, dual is better and you can set big -dcri for best results, for example on stock 1070 with "-dcri 450" I see 14.4MH/s ETH and 140MH/s LBC, both values are higher than 50% of single-mining mode. If LBC has less profit than ETH, reduce -dcri to get more ETH.
Don't forget that you can change -dcri in runtime with "+" and "-" keys and see current hashrates with "s" key.

A friend did a more testing, and ETH+LBC in R9 380 is a lot worse then ETH+ SIA
his rig stats are:
4x380
ETH/LBC = 70/55MHS
ETH/SIA  = 85/900MHS

Looks like LBC is way to GPU intensive for R9 380 and maybe other card, impact on ETH is just to huge to have any benefit mining LBC and losing on ETH side more

I don`t blame claymore for it, but the lbry algo is just like that

AMD cards always handle dual mode better than NVidia. Especially 290(X)/390(X) cards, they are the best. RX480 is good too. Other cards are not so good in dual mode.
Also Lbry is not so good for dual mode as Sia or Decred, it takes too much GPU time.

You need to recalculate again, lbry is not if any more profitable then mining sia, but with drop on ETH you are losing to mutch (4x 380 lost 15Mhs on ETH??) maybe the problem of ETH drop is more seen in multi GPU rigs

Currently, for you, it is a lot better to do sia, even without the drop in hashrate for eth.  For me, it is slightly better for sia, though an hour ago it was better to do LBRY, and yesterday probably LBRY (sia difficulty has not adjusted for recent price spike, and likely many are trying out dual LBRY, which adjusts diff every 4 minutes).  Just saying it all depends on diff/prices, but currently they are close enough that it depends on the card.

got OpenCL hang again -> no reboot.

No one can say for sure which coin is going to be more profitable.

It depends on lots of factors.

Not just the coin price right now, and the speed of mining, and the amount of coins mined... But other factors.

Suprnova not charging a fee on LBC this week means you get 1% more for example by mining at their pool.
Temp of cards dual mining in some areas (I live in Texas) means more cooling costs.
Power draw. Which one draws more power?
What kind of cards? Some of my rigs are doing better dual mining than others.
Do I need to sell coins now? Can I hold coins for profitability?
Which coin do I think has better profits?

Example. SIA was at .00000071 less than 24 hours ago. Now it's at .00000102.  It got as high as .00000129 earlier today.  If you had been mining and holding coins all this time you could sell now for the extra profits and SIA would certainly have been more profitable.

LBC has had more spikes, more activity, more news.  Even though SIA is maybe more profitable now, is it better long term?

Same with ETH.  Do you see long term profitability in ETH or do you need to sell coins now? 

Generally speaking I think we all need to wait 2 weeks until Devcon2.