the Lsi 2308 (Mustang) ROC (Raid On Chip) is available in numerous configurations. however the most importamt one is does the 2308 that you have use onboard cache.
most motherboards, and many addin cards using the 2308 chip will not have cache, as such they will be slower and usually (but not allways) have no raid 5 feature set. those that do lack cache and have raid 5 will be very slow due to the lack of onboard cache the dell perc H310 is one such card and the HP z820 is another motherboard based 2308 without cache that has raid 5 as a option
broadcom (who bought LSI) has firmware for retail LSI models which use the 2308 chip in both Raid and non raid versions
I"R" firmware is Raid capable and "IT" is HBA mode (host bus adapter)
since you are doing raid 10 which is disk mirroring and disk striping combined you should be using the "IT" firmware not the "IR" firmware on your card
which model card do you have with the 2308 chip on it?
is the card in a PCI-e 2.0 /3.0 8x slot?
your comparision link has pci-e 3.0 bus and is using MLC based SSD's which is not a valid comparision!!!
replace your mech based drives with SSD's and you to will have much much faster xfer speeds!!
your ST3750330AS drive is a sata 3gbps drive 7200rpm drives should be SATA 6gbps 7200/10k rpm