I still think that Sareln could win this. Late-game March of Trees will stop any Infernal invasion cold, and if applied offensively could wipe out any cities on Ljo borders. Against the Vamps, Sareln apparently has a crazy-long NAP with Mack. That's enough time for the Ljo to accrue a serious army if he wants to fight head-to-head, or perhaps just steal a Tower win if he wants to keep playing it passive. Sareln's biggest issue seems to be that, as far as I can tell, he hasn't actually decided on any sort of military line to emphasize, aside from PoL. Hunters and Tigers aren't going to cut it against Vampires.
Edit- I see he mentioned drafted LB armies. I think I suggested that to him in chat a few months back

(although I'm sure it would occur to anyone). Ljo LB are tough units to get one's head around. I really *want* to like them- on one hand, you can get them to champion-level strength with Iron weapons and Flaming Arrows, and they're stupidly difficult to kill in cities even after Maelstrom / Ring of Fire, and players are I think generally loathe to promote units to Cover. But on the other, they have an alarming and honestly depressing number of faults vs. Champions-
* Champs get their boosting enchantment with adepts; LB require mages.
* Champs get a special bonus vs. Melee units; LB have only defensive bonuses and a couple first-strike chances easily invalidated by a T1 spell.
* Champs can use Mirthril weapons; LB are limited to Bronze / Iron.
* If you want to get the most out of your LB, you'll want them to have Iron weapons, and if you have to research IW then why not just build Champs and save the beakers you were going to spend on Bowyers?
* LB can't take City Raider promotions.
* LB and Champs both are 80 hammers and only cost 2 pop to draft, so there's no production savings taking one over the other.
In the end, I'm sadly forced to conclude that Ljo LB, while probably capable of carrying an offense, are still inferior for that purpose compared to Champions; they're best saved for either Team games as support units for holding allied cities, or specialty units for games where having really tough defenders justifies expending 2,000-something extra beakers. That said, Sareln is Arcane & will thus surely have mages, and will probably never reach Mirthril weapons anyway, so some of the reasons to avoid LB aren't relevant here.