Cisco WAN :: QoS With ASR 1001

I've an ASR1001 with 15.1(2)S code on it connected to out ISP, we've been get some complaints about performance and I'm seeing drop on the output policy. Checking the bandwidth consumption we have plenty spare when drops are occuring, there's 300Mb/s.  Details below, any suggestions gratefully received
 
The policy is to guarantee the following bandwidth:
Outbound policy:
class 1 => 50% guaranteed
class 2 => 8% guaranteed
class 3 => 1% guaranteed
class 4 => 5% guaranteed
class 5 => 1% guaranteed
class 6 => 5% guaranteed
class  => 7% guaranteed
class 8 => 7% guaranteed
class default => not configured
 
config :
 
policy-map priority
class 1
priority percent 50
class 2
priority percent 8
class 3
priority percent 1
class 4(code)