The Oxford Learner's Thesaurus is aimed at upper-level language learners (CEF B2 and up), as it should be. I've said before that lower-level students should concentrate on the core vocabulary and not tear off willy nilly into the outback of English esoterica. In fact, the same could be said of upper-level students and a lot of native speakers of English, a reality that the folks at Oxford seem to have grasped well.
Rather than trying to be comprehensive, the Oxford Learner's Thesaurus focuses on being useful. You begin by looking up a word in the index. The entry for conquer, for example, looks like this:
conquer verbFrom there, you decide which sense of conquer you're interested in and proceed to the relevant main entry. If we choose overcome, we find the following synonyms listed: overcome, get over sth, control, bring/get/keep sth under control, beat, conquer. From these six choices, all but two words are in the most common 1,000 words of English, overcome being at the 3k level and conquer being at the 6k level: all useful words. Notice also that although the headword is listed first, the other words are listed from most to least frequent.
- INVADE (conquer a country)
- OVERCOME (conquer your fear)
- SUCCEED (conquer the US market)
In contrast, Roget's II: The New Thesaurus (third ed.) gives us: beat, best, conquer, master, prevail against, rout, subdue, subjugate, surmount, triumph over, vanquish, worst, overcome for the following frequency distribution:
- BNC-1,000 against beat best over worst
- BNC-2,000 master
- BNC-3,000 overcome
- BNC-5,000 triumph
- BNC-6,000 conquer prevail
- BNC-10,000 subdue subjugate surmount
- BNC-13,000 rout vanquish
Next, Oxford gives a brief simple explanation of the meaning of the group followed by patterns and collocations. I'm not big on teachers spending a lot of time on collocations--there's too much other more common vocabulary to learn (see here)--but presenting them here, where a student has chosen to look a word up, is more than just appropriate; it's downright helpful. Finally, we get a definition of each word with example sentences.
Other information includes: register (from slang to formal), dialect (AmE, BrE, etc.), genre (business, fiction, etc.) and more. This is the type of information a student needs to choose the right word rather than just a different one.