D-10 is said to relate primarily to career & since the 10th house represents career, it seems to me that 10th house & planets/yogas relating to 10th house in Dasamsa chart may be accurate & relevant indicators of a person's career.
As an example, I look at a particular D-10 chart where the lagna is Capricorn: Venus & Mercury are in Pisces, ie: the 9th & 10th lords combine in the 3rd house. Note 10th lord Venus exalted in watery Pisces; the combination forms a dharma-karmadhipathi yoga/Raja Yoga & is strengthened by Jupiter's aspect from Scorpio. Further, Rahu occupies the 10th house Libra.
The native had absolutely no educational & family background,
inclination or even a vague idea of pursuing a technical career in
marine radiocommunication. A series of circumstances made it happen.
The D-10 chart seems to hold the key as explained below.
The native is well employed (exalted 10th lord joining 9th lord aspected by sign lord Jupiter in D 10) as a professional working in the field of communications (3rd house) in the midst of the ocean (watery Pisces). The specific means of communication is electronic equipment/ radio (rahu). The native got his major career breakthrough in rahu bhukti of moon dasa. In D-10 chart, moon in 4th is in mutual aspect with Rahu posited in the 10th house. In D-10 chart, the lagna (Capricorn) lord is Saturn (representing oil) and as lagna lord posited in the 4th house, he aspects both lagna & 10th houses. Extremely powerful Saturn in natal chart (D1) in Aquarius perhaps makes the oil industry the field/arena whereby the native's career & worldly position gets well established.
Thus, the native's career as a professional in the field of marine radio communication happens to be in the oil industry (and not in the merchant navy). Since the native is running Rahu dasa with Rahu occupying 10th house in D-10, Rahu will probably facilitate significant career progress for the native.
each D-chart there are some Karya Houses - houses which an astrolger would refer to to determine the goodness of the affairs ruled by that particular D-chart. In the case of D-10 that would be the 1st, 6th and the 10th.
All the three houses mentioned denotes employment. The 1st is the overall employment propspects, the 6th denotes the job offer itself and the 10th the overall career trajectory of the individual.
(Mercury is the significator for the 6th and the 10th and Mercury denotes professions and career in the 10th and work for the 6th).
How about the non-Karya houses? These would generally apply to all D-charts and a summary follows of their effects for the D10.
(A) 2nd, 11th and 7th House. These houses which are the 2nd to the 1st, 6th and 10th mentioned above, impede the proper and smooth functionining of the latter houses. Why?
The 7th is the house of self-employment. If a person would rather do business, then he would not consider accpeting a job offer as indicated by the 6th house.
The 2nd house is the house of income generally. If a native's outlook in life is towards getting a job with a high pay, he would be very discriminating in his strategy of what kind of jobs to look for. In that sense it reduces his general condition of employment prospects.
The 11th house is the house of gains of your main profession. If you are always considering this issue, you may not take the proper steps or go all out in doing your job well. Your upper consideration is always - would this action of mine actually caused me to be put in a bad light which would then erode any gains that may be forthcoming. Or would my action 'rock the boat' and upset my current status quo of every month getting a fat income of my well paying job?
(B) The 12th, 3rd and 8th houses are the 3rd house to the 10th, 1st and 6th houses. The 3rd house to a house generally shows difficulties and impediments to the latter house.
The 12th shows long retirement, the 3rd shows short retirement and the 8th shows permanent retirement.
Special mention must be made of the 3rd house (as the other are Dusthana houses and their effects are generally well-known). The 3rd house in any divisional chart generally shows death-like effects. Planet lordship of this house or planets placed in it generally shows no progress. This is unlike the 3rd house in the Rasi where it is accrued in giving the individual progress through his own efforts not least of which it is also one of the Upachaya houses.
(C) The 4th house is generally credited as the seat of the throne of the chart. In the Rasi, if one wants to determine whether one can be King, both the 9th and the 4th houses are taken into consideration - with the 9th house being assessed for luck.
Similarly in the other divisional charts, the 4th house represents your stability in the matters ruled by that divisional chart. Do you have the potential to hold on to your throne? A weak 4th house in D10 is one factor that shows a person who is unable to rise up in his career.
(The Moon is the significator of the 4th house and Moon signifies fame in the 10th - a King must have a good reputation to maintain his throne).
(D) The 5th and 9th houses are trine houses and they generally give supporting boost to the career. In addition in the D10, the 9th house shows that the person would like to have a large measure of independence in his career. The 5th house is the 8th of the 10th (an important Karya house). The 5th would thus show a change of career or the start of a phase of the career for the native - generally for the better because the 5th is a trine house.
Good planets in the 5th house can help the native rise to a high position in the career - more so than even the 4th house. Whereas 4th denotes long term rise, the 5th can indicate a spectacular rise.
(Jupiter is the significator of the 5th and 9th and Jupiter signifies not only fame for the 10th together with the Moon but also prosperity and growth for the 10th).
(Sun is the natural ruler of the 5th and Sun signifies status, power and social rights for 10th house matters).