Viktor is not one of the best scaling mages at all
Viktor is a lane bully, with an obnoxious trade pattern, yes.
Viktor is NOT a scaling mage at all, compared to Ryze Syndra Veigar Asol Xerath Azir Anivia Vladimir, to name a few.
Viktor lacks mobility, his scaling on E is just bad ( 50% ap ratio on first part, most important part )
50% ap ratio on insta dmg R, 35% on tick
only DPS low short CD is Q ( Short range )
He isnt BAD in lategame, cus he is a mage, no mage is bad in lategame realistically speaking except for a few.
but he is NOT a scaling mage by any means
Viktor also offers no gameplay pattern to come back in lategame, compared to big asol R engage, syndra stuns from fog, anivia walling someone off.