Hi Charlie
I have done 8 flights with Oman Air this year and have always had two check in bags (one holdall, one Carmate rod case), totaling 27 to 29 kgs. On all 8 occasions, they have accepted the two bags combined as within the 30 kg allowance and not seemed concerned that it was two bags rather than one.
Hand luggage was a Shimano deck bag with 6 reel bodies in it, spools in the check in luggage.
I hope that helps a bit.