I've just checked a node and it runs with well under 1% CPU with ~20 connections. With ~35 connections it gets up to 5% with occasional spikes to 7, more seldom 10%. But on a very small CPU (Atom-like).
Maybe there's a difference, if compiled like you did (via QT)?
Could you try this and report back:
cd src
./autogen.sh
./configure --disable-wallet (if the wallet-functionality is not needed, for example on a P2Pool-node, or maybe NOMP also?)
make -f Makefile USE_UPNP=- USE_IPV6=- USE_QRCODE=-
(The options only to your liking, but for me it works well like above. Of course for a conventional pool or a normal user-wallet you would NOT use option --disable-wallet)
Thanks for your reply. I've recompiled everything and it seems to be working now. Must have been the UPNP or IPV6 thingy that messed up the daemon. If anyone likes to give it a try please feel free to test my pool at http://coincave.nl