Every jungler ever responds "Oh it's a waste camping a losing lane blah blah dragon blah blah snowball blah blah jungler is fautless role blah blah excuse reasoning why everything choice and decision a jungler makes is without fault and has a purpose blah blah better nerf"
On a serious note, as what I believe to be a skilled Vel'Koz player, if I am left alone with my mid lane opponent, and I am able to procure any kind of lead, left unchecked I become an over whelming mobile battleship of wtf and who fed. With patient positioning and proper mana management, I can obliterate entire minion waves with a spell rotation and do incredulous amounts of burst dmg on top of passive procs. I can often get to a point where the enemy jungler realizes ganking me puts them at risk of being both killed.
My predictive planning on placing my e during ganks has improved drastically, even champs like Lee Sin and Xin are very likely to hop up in the air when they come after me. Which garuntees at least 1 part of my w hitting, my q hitting, and a good 3-5 shots of vel's ultimate. Even when collapsed upon this generates the footing (???) he needs to reclaim the danger he was put in with the gap closing engage.
The point of this is yes agreeing with what you said. If either because of my mid laner's mistakes or because I was able to out play them, if I get ahead I will only get further ahead with Champions like vel koz. I can make the choices and decisions of where and when to place myself to prevent being in danger, and once I have taken a slight lead I won't ever let that go, if the jungler comes too late they are more food for thought.
In retrospect, being ganked and put even or perhaps even better, put behind, all my positioning and the largest mana pool in the world wouldn't put any meaning or impact to all the puple koolaid I'd spill all over the enemy team. They'd just take a sip and keep going. Gank inevitible win or lose lanes, and gank Tilt Potential lanes. If your Darius/Riven/Olaf is doing bad, gank them. Not because of their gameplay or to help your team, but probably bc there's a good chance they are close to getting angry and going on tilt, and preventing tilt does more for your team then any advantage created with a single gank.