I saw in surrender at 20 that Malzahar players feel like Malz is useless if he doesn't have his ultimate. As a long time Malz player, I have racked up so many kills from people who expect a low-damage low-threat mage and end up with a DPS DoT mage. He's a HUGE threat without his ultimate...as long as you can land your abilities. Most of the reason Malzahar's ultimate is so strong is because it forces all of his other spells to land. Any buff to Malzahar's skills is a buff to his ultimate.
Malzahar is not a good **assassin** without his ultimate. He is, however, a great mage. Please don't add too much power to his skills - his weakness isn't in that his ultimate is strong and his other spells are weak! They're in his immobility and lack of hard CC outside of his ultimate. The same applies to Sona, but nobody argues that her spells are underwhelming.
The reason Malz players might feel underwhelming when their ultimates are down is quite simply because they have spent no time actually learning how to play Malzahar. Malzahar's ult combo is important and may be all you really need to know to play and win with the character, but relying on the ult has the direct consequence of making you feel useless without the ult!
Many of the people who are speaking up about the Malzahar rework are not longtime Malz players, they are people who like to play Malzahar (mostly for the 100-0 no-counterplay burst combo). While obviously it is important to most Malz players that a 100-0 assassin playstyle is preserved, actual Malz mains are drawn more to the predictive/voidling parts of the character, rather than to a 2.5 second suppression. Changing him to be both easier and stronger is going to be very frustrating for longtime Malz players because we want to feel rewarded for playing at a high level of skill and we just...don't. Even at this point in time, there is very little that an experienced and skilled Malz player can do that a game-1 Malzahar wouldn't naturally do. :/ It's just "using the voidling to block skillshots," "landing your Q," and "not getting your ultimate interrupted."
These are just some strong feelings on the subject that I had and I really hope you don't take this the wrong way. I'm not trying to be elitist or say that those players don't understand the character. I'm just saying that sometimes these players don't realize the hidden strengths of the character and might not be able to recognize the ways in which this character can excel even without his ultimate readied.