As far as the medieval alliterative 'revival' goes, I think it's hard to talk about it in terms like success and failure. Those terms imply specific goals, which we don't really have any evidence for. There's debate, but it probably wasn't actually a 'revival' as such -- more and more scholars in recent years have become convinced by the evidence that alliterative verse was in constant use in (parts of) England from the earliest Germanic settlement straight through the Middle Ages (the last alliterative poems are attested from the 16th century). The evidence of metrics, and especially of poetic vocabulary really do point this way.
The apparent 'revival' of alliterative verse in the 14th century is probably not a revival of the art form as such, but an increase in how many such poems were written down (or composed with the pen). And it's not like there weren't alliterative poems from the intervening years. Nikolay Yakovlev has made a compelling case that Laᵹamon/Lawman's Brut should be seen as part of the alliterative tradition, and being composed c. 1200, it's nicely spaced about midway between later OE verse and the more classical Middle English alliterative poems.
The modern revival, on the other hand, is probably more properly a revival. It's a really conscious resuscitation of a metrical form that had been unused for centuries. I think it's fair to talk about 'success' and 'failure' in this sphere, insofar as it's very much a poetic experiment whose ability to result in interesting poetry is not guaranteed at the start. And in those terms, I'd call it a success. Certainly there are interesting modern English alliterative poems out there, now written over the course of a couple of generations (so it shows a certain amount of traction). Among the ones I've read, I tend to find Tolkien's the most successful -- though he worked hard on developing an effective style over the course of around a decade before he was able to achieve really compelling results. (Tom Shippey talks about Tolkien's 'steep learning curve' in his essay in Tolkien's Poetry, and I've elaborated a little on the middle portion of Shippey's timeline in a review in The Journal of Inkling Studies.)
One issue I think is really interesting with modern English verse is how nearly everyone seems to look to Old English (as is implied by your reference to Terasawa's book -- a recommendation which I highly second, by the way). This makes a certain amount of sense, since scholars have generally made better progress in understanding Old English verse than Middle. Not to say that even Old English verse has traditionally been well understood, but at least a lot of the basic work on what forms were possible, and what excluded, were identified by Sievers in the 1880's, and his 'five types' description has proven a handy and digestible rule of thumb for what to use and what to avoid. Not that many people have followed Sievers precisely in modern English -- one of the things I tried to do in my Inklings Studies piece was to outline how Tolkien had to adjust things to accommodate the very different phonological and syntactic facts of modern English.
In a way, though, it would might be interesting to see more people look to Middle English AV for inspiration. As Tolkien and others have proven, you can adapt OE verse, and end up with something that will make good modern poetry. But with Middle English the starting point is much closer: it's very similar to modern English in its relative paucity of poetic compounds, its many required unstressed words (OE could drop prepositions and 'articles' easily in a way the later stages of the languages just can't, which makes many of its rhythms hard to replicate nearly as easily), and also in the larger-scale area of how syntax relates to the metre. At least a few of the adjustments Tolkien (and others) have made to OE style have moved it to become at least a little more like ME verse.
Obviously there's a good reason why Middle English poetry hasn't been a traditional point of reference: it's been much more poorly understood. In Tolkien's day, the metre was regarded as virtually unregulated (rules had been proposed at various times, but none won wide acceptance). Most of the work on really discovering and understanding some of the detailed rules that make the metre work has been done since 1990, and a lot of the most important discoveries came within the last decade. There may well be more such discoveries to come. Even the metrical system as we understand it so far isn't very accessible to most people, since the recent research is, for the most part, published in specialist theses and journal articles: there are no general handbooks of Middle English metre.
Still, that would be an area of experimentation I'd love to see more of. I think there's a lot of potential for creating a verse style really suited to longer poems there, and it would side-step some of the awkwardness met with by many modern poets when they try to apply Old English rules (as understood by the poet) too strictly to the modern language.
It is laden with history, leading back into the dark heathen ages beyond the memory of song, but not beyond the reach of imagination.