I have noted a high ping ms there - this is due a bit load. It can be as low as 20-30 and still 'fail' with 'correct' config'.
Each GW is fed into a switch then to the pfSense box - no more than 3 feet total distance from each other, tested with different switch and routers - will sit at this figure under load.
Pinging 74.125.230.100 (google svr) via a pc routed through the pfSense box will result in a 18ms ping.
Pinging the same IP via pfSense diags results also in an 18ms ping
Rather oddly - pinging a GW via the digs results in a 0.5ms ping - so why in the 70's range with the LB tool?
More 'oddly':
As I type this, I tried half/half. First 5 having unique external IPs to ping. The first being the pfSense gateway, 200, is now responding with a 20ms ping. The following 3 are 100% loss. The fifth 100% loss but 217ms ping.
Last four 'live' as still pointing to themselves.
Changing the pfSense GW to another IP makes the first in the list go offline - with 19ms ping.
Some randomness, with some changing state with no correlation to ping ms.