Ki11s0n3: Yeah have been, I just keep dieing from those shards that he drops from the sky.
Those don't have any particular strategy to escape, he rears back when you're far away and the moment his body hits the ground they will start falling, you just have to be ready to start running towards him.
If those are the only attacks bothering you, and the spiders haven't been a problem, you might want to equip the Choir armor set. It has the highest arcane defense in the game and, aside from occasionally wriggling around, all of Rom's attacks are arcane based.
You might also want to check the gems you have equipped. Know that for the Tonitrus the best ones go from:
All ATK buff > Bolt Damage buff > Blunt Damage buff > Physical Damage buff
The status screen shows blunt damage as weaker but it's kinda bugged, the blunt one gives a way bigger buff on the Tonitrus since it's mace. This is possibly because the status screen doesn't count blunt damage but the total physical damage.