I thought that the mana bonus was a typo but it really is the ridiculous +8 bonus (which is a tad weird if not crazily mana efficient). The +1 to blue doesn’t even make sense lore-wise (not that it matters that much here) given that no iterations of Ajani so far is blue aligned). Also bear in mind that despite being able to use both red and white cards, his net mana generation is better than a standalone red or standalone white walker.
The first ability is definitely under-costed – sure, it may be worse than Jace’s first ability in some instances but lets also acknowledge that it may be a lot better than Jace’s first ability in many other instances. I just faced one and indeed at its fourth level, it does disable a creature until the beginning of your next turn
Granted, it lacks the advantages of Jace’s ability but at 3 cost (and as we have seen with Chandra), the ability is easily spammable, effectively putting a creature out of action (never mind white’s synergy with the disable mechanic).
He is portrayed as a mono green pw back from his prime yet his story puts him at post-curse-consumed (black/green).
I’d be interesting to have b/g but i think they did make him as such is because there’s already 2 black PWs and having him as such would disrupt the ballance.
I know but as another poster mentioned, Garruk is also mono coloured. In paper MtG, a multi colour deck has the advantage of being versatile (as they can put a wider range of cards if they choose to) but this is balanced by heightening their risk of being colour screwed (possibly translated as having possible mana issues). Granted, MtGPQ is different from actual paper magic (and it is a valid argument) but the point is it feels like the benefits of multicolour planeswalkers are not being balanced by any real setbacks.
In their present incarnations, multi colour planeswalkers has the benefit of having access to multiple colour and this benefit is hardly counterbalanced by any real setback. Put in another way, mono colour planeswalkers has the “disadvantage” of having access to just one colour (and colourless) with no associated benefits to it (relative to multi colour planeswalkers).