Put more cards that give you selection while causing cards to fill the graveyard and regrowrh becomes a lot more valuable. You have more oppertunity to use it, the digging will help you find it / a synergistic bomb, or you can always pitch a wasteful regrowth.
Regrowth is one of those cards like wrath of god that is super awkward at the wrong time and powerful but fair at the right.
Really helps if you can up the selection but include a lot of sorta peaky high power level cards, the sort you really do feel good about re using. Re growing the hymn or timewarp is a place you want to be, but man it's not bad the odd turn you had to recur your cheap removal or fetch land when you need it or just to get a bit of work out of the card.
There are a lot of ways to make regrow better in your cube, or really any more situational card, add more selection, make sure spells are cheap and plentiful and interacting often and forego similar cards for more of the kinds that interact with important zones like the graveyard. God I just love how Thirst For Knowledge gives all my cards cycling. I'm so much more likely to go out on a limb on neat synergy. Regrowth might be better with big splashy effects but you really only need a couple to capitalize on.