Issue's with poller / discovery

Ive got some issues with the poller in a fresh LibreNMS installation on CentOS.
We are only running network devices of Cisco , some of the devices got a pretty high poller time 120-160 .
Also devices already discovered lose their type and icon brand and after manually rediscovering it will show up as it was before. There are also gaps in data graphs. This happen with all hosts even the localhost pops up with a warning when running the ./validate.

“Some devices have not been polled in the last 5 minutes.
You may have performance issues. Check your poll log and see:

I’ve installed RRDcached and gone through to disable certain pollers and changed the snmp timeout and retry interval. Nothing seem to work and devices pop up as down while their are pingable and while i can successfully execute an snmpwalk on the device.

First i thought it was the installation of librenms so i downloaded the Ubuntu VM and deployed this with a full Installation . But even this turns out with the same issue.

I am running the VM on a VMware Vsphere 5.5 server with 2 sockets x 4 vcpu’s
got 32 GB RAM and 300GB hdd assigned to it.
Could someone tell me what could change to increase the performance?

Just to add some information , it seems that all the devices that have a high poller time are Cisco 887VA’s with DSL interfaces. The port poller for these devices takes alot of time.

You will need to pastebin the output of ./poller.php -h HOSTNAME -d -r -f

Here by the output of the poller.
The ADSL-LINE-MIB seems to take pretty long because there was no response given.

I disabled ADSL polling globallly and went from 150 seconds polling time to 8 . I dont really mind about the information of the ADSL controllers. This also made my installation more stable and devices dont seem to show up in the ./validate as not polled within 5 minutes.