Luck and drop rates in Runescape

Luck or drop rates? What is the main thing?

Mathematician in me tells that drop rates are most important, while my 5 year playing experience screams that drop rates mean nothing and only luck matters. And I think I'll go with the luck...

I know drop rates are out there and I just recently posted drop rates for ancient effigies, but they never seem to be even close to the reality. At least not for me.

I never relied on drops for getting money in Runescape and while I was always well off from money stand point (especially after introduction of the GE), it kind of bothered me that I would never get any kind of big and exciting drops from all those monster hordes I've been killing on my slayer assignments. I started playing in 2005 and got my first "dragon" drop sometime in 2009 (I am not counting dragon boots which are not rare). It was Dragon Med helm and I sold it for 60K. I got another helm later on as well as Dragon Spear which gave me another 90K or so. I also had a piece of Black Mystic which raised about 500K at the time. But that was it.

Clues were rather empty too. Maximum I would get from lvl 3 clues was around 700-800K (which is admittedly not bad, but nothing extraordinary).

And no Champion scrolls. I did get dragon head from KBD last year, though.

I kind of got used to it, but then came ancient effigies and I simply couldn't get one, no matter how many slayers assignments I did. In fact I completed more than 30... I started to worry: "was I in some super secret Jagex's black list or something?!!"

And then suddenly 3 days ago my luck turned around. First I got two whips from one assignment (7M). Then Saradomin platebody and Guthix full helm in one clue (3M), then an ancient effigy (finally!) and immediately after that Fox Mask from another clue (18M).

So what about drop rates? 5 years of nothing and 3 days of plentiful?
Pure luck and nothing else!