You might need to play Malphite to understand how he works a bit more...
Restricting his ult to a specific range like Ryze is pretty much pointless, and would destroy his playability. His Ult is pretty much all he has going for himself considering it's the only one of its kind. Take away that identity of being an unstoppable moving mountain and all you have is a garbage Armor melee tank with a slow and AS slow (when in melee range).
If you took away his ability to ult next to himself then you'll take away his ability to stay in the fight or lock down opponents. It's used as initiation or as a lock down. Restricting it to initiation range only is pretty much pointless and would make his teamfighting garbage since a lot of teams like to work around his ult and his ult's range.
Also, his ult does offer counterplay ;P It's called paying attention and not grouping up when there's a malphite on the enemy team. If you group you betcha he's going to ult your face for his team.
Mobile champions are his bane too, and the fact that a single summoner spell can instantly negate his ult is pretty lame. But it happens much like
counters a lot of drain tanks/lifesteal champs.
In all honesty he's in an okay place right now. He's still viable top and Jungle, but struggles hard against ranged champs or tank shredders like Vayne/Quinn.