I'll help you out man, don't seem to get it yet.
So Urgot's Q doesn't do that much damage or slow enough for Urgot to catch literally anyone. It slows them by enough for him to get close enough to get a basic attack in.
That said, the only way he is gonna land E is just that, by landing E itself. Essentially, Urgot is a melee champion with 150 more range (compared to the +275 range typical of other ranged champs). He doesn't function in any way like a ranged champion does.
Now here's the argument brought up in the OP:
- Cassiopeia (or another spammy mage) procs Conqueror in 1s and can keep it up indefinitely so long as the opponent comes into I think 600 range at all at least once every 5s.
- Urgot procs it in a EQ,AA,W1W2W3W4W5. Excluding the EQ time, the AA -> W5 takes a total of ~1.3 seconds. So not only does he proc it slower and not have it up for the majority of his combo (to which he also has moderate cooldowns), but he can only also do this reactively rather than aggressively.
Previously Conqueror was full-stacked on the 2nd W hit, a full second faster than the current one.