A casual deck that happens to contain two cards that go infinite should not be rated the same as a tuned combo deck that can assemble the combo by turn 4
She makes all of your X spells one mana cheaper for each +1/+1 counter on her, and she gains two +1/+1 counters each time you cast an X spell
On its own, it gives you and your permanents hexproof for the turn, but if you gift an opponent a card, your permanents also gain indestructible, which is perfect for dodging board wipes
Leyline of Vitality Leyline of Vitality is great for lifegain decks
Since Timeless has both fetchlands and Mishra's Bauble, it is easy to get two of the four card types needed into your graveyard to turn Dragon's Rage Channeler into a 3/3 flyer
Altar of Bhaal springs to mind, letting you trade a token on the battlefield to get back a Zombie creature card that ended up in the graveyard