Personally, I think the syllabus for Deep diver is much too weak and misses many opportunities to effectively train divers for safe deep diving. I now recommend the 'Tec40' as an alternative.
Tec40 versus Deep Diver
Outcome
1. Both courses qualify to 40m/130ft
2. Both courses minimum 4 dives
Tec40 Pros
1. Redundant gas system (large capacity single with 'H' valve, or single plus pony, or doubles)
2. Gas management taught in detail
3. Dive planning taught in detail
4. Nitrox to 50% as an option for safer, more conservative off-gassing on ascent
5. Foundational skills (buoyancy/trim/situational awareness) developed to a high level
6. Multiple emergency drills and protocols taught
7. Conducts 10 minutes (non-accelerated) decompression, rather than 8 minutes 'simulated' emergency decompression
8. Additional communication skills taught
9. DSMB deployment taught
10. Substantially more theory (EANx, DCS, safe deep diving mindset, team skills, narcosis) etc
Tec40 Cons
1. Slightly more equipment needed for Tec40 (including some mandatory redundancy)
2. Requires prerequisite AOW and Nitrox qualifications
3. PADI website says prerequisite of Deep Diver also, but instructors can accept "or show proof of at least 10 dives to 30 metres/100 feet." according to the instructor manual.
4. Diver must have experience of "a minimum of 30 logged dives, of which at least 10 dives were made with enriched air nitrox deeper than 18 metres / 60 feet".
IMHO, the above prerequisites aren't unrealistic, or overly demanding, if someone wants to dive below 100ft/30m...
The Tec40 course is described as 'covering the gap between recreational and technical' diving. It can be run very much as an entry-level technical program (with doubles) or as a 'tecreational'-style serious deep diving course for recreational depth limits (using less demanding redundant gas/equipment options).
Most experienced divers would state that the Deep Diver course "can be okay" providing the instructor supplements the training with additional knowledge and skills. The Tec40 achieves this as a matter of course. An instructor qualified to teach Tec40 is also likely to be significantly higher qualified and more (deep diving) experienced than a recreational instructor 'signed off' after 1 day training to teach Deep Diver...