Oh god, I don't need any of the loot from Titan raid so I've run it exactly 1 time on any toons. I much prefer fighting stuff to doing puzzles and hanging on ladders.
I'm honestly new enough where I haven't really had the opportunity to have that grind yet. I've only hit 40 on a couple toons for a couple raids and the only raid item I really, REALLY want on any toon that I haven't pulled is the Torc - and that's after 9 combined raids on two toons.
So I haven't felt this sting really but I can understand how frustrating it could get. And it's not like having missed out on your 20th makes things any easier on your 40th...it's the same chance yet again. And each 20 is a minimum of two months.
So yeah, if you put in two months of raids you should have a better chance than you have now of pulling what you want. And every two extra months of raids should raise that chance even higher.