I see it being useful in Limited, and to get up to a reasonable creature count in a Gremlins deck
Ugin, the Spirit Dragon Ugin doesnt sport quite the fabulous price tag that the original Grim Tutor has, but for a far more popular and widely-played card, it was still seriously undersupplied
The former will have an opponent lose 1 life whenever they cast or copy an instant or sorcery spell
The most obvious, but also worst argument: in Magic, you lose when you run out of cards
The life matters so infrequently and is only an enticing aspect of the card in control and midrange decks, of which you find few in Boros colours
However, if a Lion Umbra you control is attached to a creature you don't control and that creature has no Auras controlled by that creature's controller attached to it, no Equipment attached to it, and no counters on it, Lion Umbra will be put into its owner's graveyard due to being attached to an illegal object the next time state-based actions are performed