It really depends on what you're fighting. If you're fighting something you can 1 or 2 shot, then not so much. If you're fighting a paragon Balron, then you're going to spend most of the fight out of mana, which will make it take 3x as long to kill as if you had mana leech. Even Peerless, which can take 10 minutes with a good group, will have you completely out of mana within the first couple of minutes. Your suit actually has a pretty high MR, which is awesome, but even with that in any prolonged fight, you'll find that spamming LS isn't going to be possible, not to mention the Chiv spells.
Try this, take an Undead slayer bow without mana leech and go take on a paragon Lich Lord. Then take a Demon slayer without it and try a paragon Balron. Even a paragon Rotting Corpse would be good for testing. You'll see how fast you run out of mana when you're getting hit for 50ish on a regular basis with poison, curses, and everything else that you'll get pounded with from the higher end stuff added into the mix.